Some 100,000 people have fled their homes in north Syria, the UN reports, as Turkey presses on with its cross-border offensive on Kurdish-held areas.
Many people are sheltering in schools or other buildings in Hassakeh city and the town of Tal Tamer, the UN says.
Turkey took action on Wednesday after US President Donald Trump pulled American troops out of the area.
At least 11 civilians have died. Humanitarian groups say the number of people affected will rise further.
Dozens of fighters from the Kurdish-led Syrian Democratic Forces (SDF) and pro-Turkish factions have been killed. The first death of a Turkish soldier was confirmed by Turkey’s military.
Analysts say the US withdrawal in effect gave Turkey the green light to begin its cross-border assault.
Much of the region has been outside the control of the Syrian government as a consequence of the civil war which began in 2011. It has been controlled by the SDF since 2015.
The SDF have been key allies of the US in the battle against the Islamic State (IS) group but Turkey regards the Kurdish militias of the SDF as “terrorists” who support an anti-Turkish insurgency.
Turkey defended its offensive as a bid to create a “safe zone” free of Kurdish militias which could also house Syrian refugees.
“We will not stop it no matter what anyone says,” President Recep Tayyip Erdogan said on Friday.
One major concern for the international community is the fate of thousands of suspected IS prisoners, including many foreign nationals, being guarded by Kurdish-led forces in the region.
On Friday, IS said it had planted a car bomb that killed six people – civilians and members of the security forces – in the border town of Qamishli on Friday.
Meanwhile, US media report that an explosion occurred near a US base in Kobane, but no injuries have been reported.
On Thursday, Turkish troops partly encircled the towns of Ras al-Ain and Tal Abyad.
But while the Turkish military said its operation was going to plan, Kurdish sources and activists from the Syrian Observatory for Human Rights (SOHR) said the offensive had not made much progress.
Turkish warplanes have struck targets in both towns, and video footage has shown columns of smoke rising above them. Tal Abyad’s only public hospital has been forced to close.
The Kurdish Red Crescent said there had been 11 confirmed civilian deaths so far and 28 serious injuries, mostly in Ras al-Ain and another border town, Qamishli. Some are children.
At least five people, including a Syrian baby, were reportedly killed in Kurdish shelling of Turkish border towns.
The SOHR reported at least 29 deaths among the SDF and 17 from among pro-Turkish Syrian rebels (known as the Syrian National Army), as more than 10 villages fell into Turkish hands.