Turkish President Recep Tayyip Erdogan said the operation was to create a “safe zone” cleared of Kurdish militias which will also house Syrian refugees.
The offensive was launched just days after President Donald Trump withdrew US troops from the border area.
The unilateral decision has been widely condemned, with the European Union urging Turkey to end its offensive.
European Commission President Jean-Claude Juncker called on Turkey to stop its military operation in northeast Syria, adding it could not lead to ‘good results.’
The UN Security Council’s President, has appealed to Turkey to “protect civilians” and exercise “maximum restraint” in its military operations in Syria.
The UNSC chief expressed hope the council could meet quickly on the situation but stressed it was up to drafters of resolutions on Syria to convene such a session.
The Arab League is also convening an emergency meeting on Saturday to discuss Turkey’s offensive against Kurdish forces in Syria.
Following a request by Egypt, the foreign ministers of 22-member countries will gather in Cairo on Saturday “to discuss Turkish aggression on Syrian territory”.
The announcement came after Turkey launched airstrikes and artillery fire along the border with war-torn Syria earlier in the day, drawing international condemnation.
Meanwhile, thousands of Syrians fled on foot and by car from border towns of Tel Abyad and Sari Kani.
Amid deepening humanitarian concerns, UN secretary-general Antonio Guterres urged all parties in northeast Syria to exercise maximum restrain and protect civilians.