Heavy fighting is reported in northern Syria on the second day of a Turkish offensive into Kurdish-held areas.
Turkey says it has seized a number of designated targets and killed dozens of Kurdish militants.
Tens of thousands of people are reported to be fleeing their homes, and Kurds report several civilian deaths.
Turkey says it wants to create a “safe zone” cleared of Kurdish militias which will also house some of the millions of Syrian refugees it hosts.
The long-planned Turkish offensive began after President Donald Trump withdrew US troops from the area, which has been held by the Kurdish-led Syrian Democratic Forces (SDF). The SDF have been key US allies in the battle against the Islamic State (IS) group but Turkey regards their dominant Kurdish militias as terrorists.
Many in the US, including some of Mr Trump’s Republican allies, saw the withdrawal as effectively giving a green light for Turkey, although Secretary of State Mike Pompeo on Wednesday denied this. The SDF said they had been “stabbed in the back”.
Mr Trump tweeted on Thursday that he was trying to end “endless wars” but added: “I say hit Turkey very hard financially & with sanctions if they don’t play by the rules! I am watching closely.” He also said he was “talking to both sides”.
The offensive has drawn international condemnation. The UN Security Council is due to discuss it on Thursday at the request of its current five EU members – the UK, France, Germany, Belgium and Poland.
Turkey’s President Recep Tayyip Erdogan has strongly defended the incursion, threatening to send the Syrian refugees it hosts to Europe if the Turkish offensive is described as an occupation.