The UN has expressed concern over a radical EU-Turkey plan to ease the migrant crisis, saying it could contravene international law.
Under the plan, all migrants arriving in Greece from Turkey would be returned and for each Syrian sent back, a Syrian in Turkey would be resettled in the EU.
The UN's refugee agency said any collective expulsion of foreigners was "not consistent with European law".
Amnesty International called the plan a death blow to the right to seek asylum.
The deal, discussed at a summit in Brussels on Monday, has not been finalised and talks will continue ahead of an EU meeting on 17-18 March.
Europe is facing its biggest refugee crisis since World War Two. Last year, more than a million people entered the EU illegally by boat, mainly going from Turkey to Greece.
Most of them were Syrian, fleeing the country's four-year civil war. Another 2.7 million Syrian refugees are currently in Turkey.
What's in the EU-Turkey proposal?
The EU heads said "bold moves" were needed to tackle the crisis, and made the following proposals:
All new irregular migrants crossing from Turkey to the Greek islands will be returned to Turkey, with the EU meeting the costs. Irregular migrants means all those outside normal transit procedures, ie without documentation. The term "illegal migration" usually refers to people smuggling
In exchange for every returned Syrian, one Syrian from Turkey will be resettled in the EU
Plans to ease access to the EU for Turkish citizens will be speeded up, with a view to allowing visa-free travel by June 2016
EU payment of €3bn ($3.3bn; £2.2bn) promised in October will be speeded up, and a decision will be made on additional funding to help Turkey deal with the crisis. Turkey reportedly asked for EU aid to be increased to €6bn
Preparations will be made for a decision on the opening of new chapters in talks on EU membership for Turkey
The BBC's Selin Girit says that says Turkish media have hailed the plan - particularly the visa-free access - but critics have accused the EU of turning a blind eye to Turkey's human rights record.
How have leaders reacted?
European Council President Donald Tusk insisted the leaders at the summit had made a "breakthrough", and he was hopeful of concluding the deal in the next week.
However, German Chancellor Angela Merkel was more circumspect, saying: "It is a breakthrough if it becomes reality."
Turkish Prime Minister Ahmet Davutoglu said Turkey had taken a "game-changing" decision "to discourage illegal migration, to prevent human smugglers, to help people who want to come to Europe through encouraging legal migration".
What are the legal concerns?
Vincent Cochetel, the UN's regional co-ordinator for the refugee crisis in Europe, said: "An agreement that would be tantamount to a blanket return of any foreigners to a third country is not consistent with European law."
Amnesty International said the plan was "wrought with moral and legal flaws".
Amnesty's Iverna McGowan said: "EU and Turkish leaders have sunk to a new low, effectively horse-trading away the rights and dignity of some of the world's most vulnerable people."
The EU believes the legal questions will be covered by declaring Turkey a "safe third country" for return. Amnesty says it strongly questions the whole concept of "safe third country".
Turkey is also not a full member of the Geneva Convention, which could raise more legal questions.
Can the return system work?
The system spelled out to the BBC by EU Commission spokesperson for migration Natasha Bertaud would see all migrants rescued in Greek waters taken to a Greek island for screening.
Irregular migrants would then be returned to Turkey to be screened again and "if they have no right to international protection" - which currently covers only Syrians - sent back to their country of origin.
All migrants rescued in Turkish waters would be taken back to Turkey, which would decide their status.
Serious questions remain. What will happen to the thousands of migrants already in Greece, which has struggled to shelter and register them?
The biggest problem will be the migrants themselves - having risked their lives and invested much of their money, will they not simply try other routes?
Vincent Cochetel said: "As long as the conflict is not solved, it's a myth to believe that people will not try to leave."
What are the other obstacles?
There is major opposition among some EU members to compulsory migrant quotas. Hungary says it vetoed the Turkish resettlement proposal on Monday and may do so again at the next EU meeting.
Turkey's bid for EU membership is another thorny issue, not helped by the recent wrangle over the court-ordered seizure of the opposition Zaman newspaper.
More problematic is Turkey's request for visa-free access for all its citizens to the EU's Schengen zone, which it hopes to achieve by June. This may draw a lot of opposition.
The future of Schengen - which allows passport-free travel in a 26-nation zone - is already in doubt, given that eight of its members have introduced temporary border controls.
source: BBC WORLD NEWS
A Catholic priest of Congolese origin has resigned in southern Germany after getting death threats and racist abuse.
Olivier Ndjimbi-Tshiende, 66, told parishioners of his decision during a church service on Sunday in Zorneding, a small town near Munich in Bavaria.
A statement on the parish website (in German) said: "We are shocked and saddened by these [death] threats." He began preaching in the town in 2012.
Tensions had arisen between him and two local conservative CSU politicians.
Fr Ndjimbi-Tshiende criticised language used by local CSU leader Sylvia Boher in October. She had spoken of an "invasion" by Eritrean "refugees from military service".
The surge in asylum seekers entering the EU includes many Eritreans fleeing military service, to avoid years spent in deplorable conditions for little or no pay.
After Fr Ndjimbi-Tshiende's intervention a CSU friend of Ms Boher, Johann Haindl, lashed out at the priest with a racist insult.
Both CSU politicians were heavily criticised over the affair and resigned from their party posts.
Police investigation
The Christian Social Union (CSU), based in Bavaria, is politically allied with Chancellor Angela Merkel's Christian Democrats (CDU).
Police are now investigating a suspected crime of racial incitement and abuse targeting Fr Ndjimbi-Tshiende.
Germany is struggling to accommodate record numbers of non-EU migrants - 1.1 million asylum seekers were registered last year.
German media say the priest, born in the Democratic Republic of Congo, had received five death threats.
An online petition (in German) has been launched urging him to stay in Zorneding. But the Catholic Church Archbishopric in Munich plans to transfer him to a new post on 1 April.
The local broadcaster BR says that in 2014 a school project to help 35 child refugees in Zorneding triggered a barrage of xenophobic emails.
Collected from : BBC WORLD NEWS
European Union leaders are holding a crucial summit with Turkey on ways of dealing with Europe's worst refugee crisis since World War Two.
The EU is pressing Turkey, through which many migrants transit, to take some back in return for $3.3bn in aid.
The Brussels talks have been extended into a working dinner between the 28 EU leaders and Turkish PM Ahmet Davutoglu.
Meanwhile Turkey's President Recep Tayyip Erdogan accused the EU of failing to deliver on the promised aid.
"It's been four months," Mr Erdogan said in Ankara. "My prime minister is currently in Brussels. I hope he will return with the money."
Turkey is currently sheltering more than 2.5 million refugees from the civil war in neighbouring Syria.
The EU wants Turkey to take back migrants who do not qualify for asylum and do more to patrol its own waters.
In exchange for this, the Turkish government is reportedly asking for more EU money, a faster path to towards EU membership, as well as speeding up plans to allow Turks visa-free travel in Europe.
Last year, more than a million people entered the EU illegally by boat, mainly going from Turkey to Greece.
Many migrants leave Greece in an attempt to reach northern Europe, but eight countries have introduced temporary border controls.
Some 13,000 migrants are currently stranded in northern Greece, after Macedonia closed its border to all but a trickle.
The future of the Schengen agreement - which allows passport-free travel in a 26-nation zone - is on the agenda, as the leaders are anxious to save a system thought to bring billions of euros to Europe's economy every year.
'Solid opt-out'
The summit was initially due to be in two parts - the first session from 12:00 GMT involving Turkey, while in the afternoon EU leaders will seek to reach a common approach.
After the talks started, however, the EU announced that a working dinner would be added to discuss "new ideas" offered by Turkish Prime Minister Ahmet Davutoglu.Earlier, Mr Davutoglu said Turkey was "indispensable" for the EU, just as Europe was for Turkey.
German Chancellor Angela Merkel said she anticipated a "difficult discussion", as a rift emerged among EU powers on the closure of the main route through the Balkans.
A draft summit communique reported by journalists on Sunday declared that "irregular flows of migrants along the Western Balkans are coming to an end; this route is closed".
But Mrs Merkel said: "Today is about finding a lasting solution together with Turkey... trying to find a way to stop illegal migration and improving the living conditions for the refugees."
A German government source told the BBC there was no point saying the route was closed when 300-500 people still arrived in Germany every day this way.
Analysis: Chris Morris, BBC News, Brussels
This summit has hardly started and already it has been extended. There will be a second session with Prime Minister Davutoglu and all 28 EU leaders over dinner.
The EU is asking for a lot from Turkey, and Turkey is now asking for more in return. Hence the irony that the fate of the EU's migration policy, and its future cohesion, lies in the hands of a country it has been keeping at arms length for years.
Without active Turkish co-operation, there is no chance of reducing the flow of refugees and migrants arriving in the Greek islands. And without that happening, the rest of the policy starts falling to pieces.
UK PM David Cameron said there was "no prospect of Britain joining a common asylum process in Europe".
"We have an absolutely rock-solid opt-out from these things," he said.
The EU said last October it would relocate 160,000 asylum seekers, mainly from Greece and Italy, but there was strong opposition among some members and fewer than 700 migrants have moved.The union may now overhaul its Dublin Regulation, which requires asylum seekers to lodge claims in their EU country of arrival, and instead adopt a centralised system for processing applications.
EU leaders were also expected to raise the issue of the Zaman newspaper. On Friday, a Turkish court ordered the seizure of the opposition journal, increasing fears for media freedom. Two days later it was publishing pro-government articles.
'All we do is sleep'
More than 2,000 migrants, mostly from Syria, Iraq and Afghanistan, continue to arrive daily in Greece from Turkey.
The Idomeni crossing on the Greece-Macedonia border has become the latest focus of the migrant crisis.
One camp resident, Syrian refugee Narjes al Shalaby, told AP news agency: "All we do here is sleep, wake up, sleep," she said. "We get hungry, we wait in the queue for two hours for a sandwich, we come back, we sleep some more."Separately, Nato says it is expanding its naval mission against people-smuggling in the Aegean Sea to cover Turkish and Greek territorial waters.
EU Commission spokesperson for migration Natasha Bertaud told the BBC all migrants rescued in Greek waters would be taken to a Greek island and screened.
All economic migrants would then be returned to Turkey to be screened again and "if they have no right to international protection" sent back to their country of origin.
All migrants rescued by Nato in Turkish waters would be taken back to Turkey.
this news is a copy-write of BBC World news
