Tens of thousands of Syrians are fleeing toward the Turkish border to escape heavy fighting near the northern city of Aleppo.
Turkish Prime Minister Ahmet Davutoglu said on February 4 that up to 70,000 may be heading to the border, while a monitoring group put the number at about 40,000.
Syrian government forces, backed by Russian air strikes, have advanced near the country's largest city.
Around 300,000 people are believed to be trapped in Aleppo after the rebels' main supply route was cut off by government forces in an offensive that torpedoed UN-mediated peace talks in Geneva this week.
The breakdown in negotiations came as Moscow and Ankara traded barbs over the escalating crisis in Syria.
Davutoglu has accused Russia and other supporters of Syrian President Bashar al-Assad's regime of committing "war crimes" in Syria.
Meanwhile, Russia's Defense Ministry spokesman Igor Konashenkov responded to Davutoglu's criticism by accusing Turkey of "intensive preparations for military intrusion" into Syria.