An upcoming meeting between Presidents Vladimir Putin and Recep Tayyip Erdogan, may come after a meeting of the Security Council, to discuss the growing tensions there.
The United States, Germany, Britain, France, Belgium, Estonia and the Dominican Republic have called for a meeting of the Security Council, while a number of these countries announced support to Turkey, in light of threats to release immigrants.
Videos spread on Twitter showing groups of immigrants, including prisoners released by Turkey, on their way to Europe, following Ankara's announcement that it would no longer block the migrants' path.
Turkish President Recep Tayyip Erdogan, whose country hosts more than 3.5 million Syrian refugees, has long threatened to "open doors" for millions of refugees eager to flee to Europe unless more international support is provided.
The Turkish announcement came in response to the killing of about 33 Turkish soldiers in an air strike launched by the Syrian army in Idlib.
The migrants headed to the land borders with Greece, where they boarded minibuses and taxis from Istanbul.