Turkey has warned the EU that millions more refugees could flee Syria as the civil war intensifies, European Council President Donald Tusk has said.He said Russian and Iranian engagement in Syria was making a victory for President Bashar al-Assad more likely.
According to Turkish estimates, it could mean another three million refugees from Aleppo and the area.
The International Organization for Migration says it has so far had no reports of more people leaving Syria.
"Violence and increased military activity breed displacement of civilians," IOM spokesman Leonard Doyle told the BBC.
He said his organisation was currently checking the situation on the ground, adding that Mr Tusk's comments were "speculative".
In other developments:
- Austrian Chancellor Werner Faymann is visiting the Greek island of Lesbos to see the impact of the migrant crisis on one of the main entry points to the EU
- UK Home Secretary Theresa May is expected to say that Britain does not need immigration in the hundreds of thousands every year because this makes building a cohesive society impossible
- Nearly 100 migrants are reported to have died in the Mediterranean off Libya since Sunday, the IOM says, citing unconfirmed reports from the Libyan Red Crescent
- The body of a man - believed to be from Eritrea - was found after a fire broke out on Monday in a shelter for asylum seekers in eastern Germany, reports say
'We need Turkey'Addressing the European parliament on Tuesday, Mr Tusk said: "During my visits to the region whoever I spoke to - presidents or refugees in the camps - in Turkey, Jordan, or Egypt warned me against one thing: a potential victory of Assad's regime - more likely today because of Russia's and Iran's engagement in Syria - will result in the next migratory wave.
"Yesterday, this message was confirmed by (Turkish) President (Recep Tayyip) Erdogan. According to Turkish estimates another three million potential refugees may come from Aleppo and its neighbourhood."
Russia began its air strikes in Syria on 30 September, saying it was targeting Islamic State (IS) militants at the request of Mr Assad's government.
The West says Russia is also hitting non-IS rebels - a claim denied by the Kremlin. There have been reports that a number of Syrian civilians have been killed in the Russian strikes,
In Brussels, Mr Erdogan and EU leaders agreed to finalise an action plan with Turkey in the coming days to deal with the refugee crisis.
"It is clear that we need Turkey. The Commission will come to its aid," European Commission chief Jean-Claude Juncker said.
He also hailed Turkey for having admitted 2.2 million Syrian refugees.
But any such action plan could be torn to shreds if millions more refugees emerge from the Syrian civil war, the BBC's Chris Morris in Brussels reports.
Hundreds of thousands of migrants - many of them fleeing conflicts in the Middle East and North Africa have already arrived in the EU this year.
Last month, the 28-member EU agreed plans to relocate 120,000 migrants over the next two years.