NATO Secretary General Jens Stoltenberg expressed "serious concerns" on Friday about Turkey's ongoing operation against Kurdish forces in Syria and called for "restraint". 

Russian President Vladimir Putin said Friday that Turkey's military operation in Syria could lead to the revival of the Islamic State group in the region.

Putin said Kurds who were guarding thousands of imprisoned IS fighters are now fleeing.

Turkish and allied forces faced stiff Kurdish resistance on Friday as they battled to seize key Syrian border towns, on the third day of a broad offensive that has sparked a civilian exodus.

Turkish President Recep Tayyip Erdogan warned the EU on Thursday that Ankara would allow millions of refugees to head to Europe if the bloc criticised Turkey's military offensive in Syria. 

Syria's Kurds said Thursday that Turkish bombardment had hit a prison they use to house captured Islamic State group fighters, despite Ankara's pledge to do nothing to undermine the campaign against the jihadists.

The head of a Turkish opposition news site was arrested Thursday, his employer said, as part of a crackdown on critics of the military operation launched in Syria a day earlier.

US President Donald Trump has warned Turkey against going too far in Syria, just a day after giving Ankara an apparent green light to invade its southern neighbor and sparking panic among Washington's Kurdish allies.

The US pulled back 50 to 100 "special operators" from Syria's northern frontier, where they have served as a buffer preventing a long-planned assault by the Turkish military against Kurdish forces in Syria. 

Turkey's preparations for an offensive in northern Syria have been "completed", the defence ministry said Tuesday, after confusing signals from the US over whether it would allow an operation.

US President Donald Trump ordered the withdrawal of US troops from Turkey's border with Syria after a phone call with his counterpart Recep Tayyip Erdogan. 

US troops in northern Syria will no longer be near the border with Turkey, nor will they support Ankara's "long-planned operation" into the country, the White House said on Sunday.

EU member Cyprus on Friday accused Turkey of defying the bloc by sending another drilling ship to operate inside its waters in what it termed a 'severe escalation.'