The EU's border protection agency Frontex said Sunday it is on "high alert" on Europe's borders with Turkey as thousands of migrants seek to enter the bloc, adding it is deploying support to Greece.
"We... have raised the alert level for all borders with Turkey to high," the Frontex spokeswoman said in a statement to AFP.
"We have received a request from Greece for additional support. We have already taken steps to redeploy to Greece technical equipment and additional officers," she added.
Thousands of migrants were getting unimpeded passage across Turkey to the borders of European Union member countries Greece and Bulgaria.
Turkish President Recep Tayyip Erdogan said he "opened the gates" for them after dozens of his troops were killed in airstrikes in northern Syria by Damascus's Russian-backed regime.
He is seen to be using the migration flow to try to pressure the EU and its NATO member states to lend him support in Turkey's military operation in Syria.
Frontex said it was monitoring closely the situation along the Greek and Bulgarian borders with Turkey and "we are looking into other ways of supporting EU countries bordering Turkey".
The statement added: "We are in close contact with Greek authorities regarding additional support we can provide in this rapidly evolving situation."
It said it was also monitoring the situation in Cyprus, an EU member state whose northern part is controlled by Turkey and only recognised by Ankara.
The agency noted that it was already staffing operations in Greece and Bulgaria. Its current biggest deployment is in the Greek islands, where it had 400 personnel, and a small contingent in the Evros region on the Greek-Turkey border. It currently has 60 officers in Bulgaria, it said.