Casualties are increasing as Turkey presses on with its cross-border offensive on Kurdish-held areas of northern Syria.
At least 11 civilians have died and dozens of fighters from the Kurdish-led SDF and pro-Turkish factions have been killed, reports say.
The first death of a Turkish soldier was confirmed by Turkey’s military.
Tens of thousands of people have fled homes in the area, as international calls to halt the attack increase.
Republicans in the US House of Representatives have announced plans to introduce a sanctions bill against Turkey, and President Donald Trump has offered to mediate.
Turkey moved into northern Syria on Wednesday after the president pulled US troops out of the area.
Critics say the US withdrawal effectively gave Turkey the green light to begin its cross-border assault.
Turkey has defended the offensive as a bid to create a “safe zone” free of Kurdish militias which could also house Syrian refugees.
Turkey regards the Kurdish militias of the Syrian Democratic Forces (SDF) – which have controlled the cross-border areas – as “terrorists” who support an anti-Turkish insurgency.
The SDF have been key allies of the United States in the battle against the Islamic State (IS) group.
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.
What’s the latest on the fighting?
On Thursday, Turkish troops encircled the border towns of Ras al-Ain and Tal Abyad.
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.
Activists from the Syrian Observatory for Human Rights reported at least 29 deaths among the SDF and 17 from among pro-Turkish Syrian rebels, the Free Syrian Army, as more than 10 villages fell into Turkish hands.
In a later report, they said that seven members of the pro-Turkish forces had been killed as the SDF retook a village in Tal Abyad region, one of them a Turkish soldier.
Turkey’s military confirmed a soldier’s death and said three others had been wounded.
Turkey’s Anadolu news agency said late on Thursday that 228 Kurdish militants had been “neutralised” since the start of the operation.
Meanwhile tens of thousands of civilians are fleeing their homes, and aid agencies fear the exodus could reach hundreds of thousands.
Turkey wants to create a “safe zone” running for 480km (300 miles) along the Syrian side of the border but says it will not advance deeper than a planned 32km limit.
How is the offensive affecting people?
Some 64,000 people have already reportedly fled their homes, the International Rescue Committee aid organization said. The UK-based monitoring group, the Syrian Observatory for Human Rights, gave a similar figure.
The IRC’s Misty Buswell said: “If the offensive continues it’s possible a total of 300,000 people could be displaced to already overstretched camps and towns still recovering from the fight against IS.”
Another group of 14 humanitarian organisations, including the Mercy Corps, warned the figure could be 450,000.
What has the reaction been?
The UN Security Council discussed the situation on Thursday at the request of its current five EU members – the UK, France, Germany, Belgium and Poland.
The five called on Turkey to halt its military offensive, saying “renewed armed hostilities in the north-east will further undermine the stability of the whole region, exacerbate civilian suffering and provoke further displacements”.
UN Secretary General Antonio Guterres expressed his “deep concern” at the rising violence.
Turkey for its part said it would take responsibility for the IS prisoners it found during its offensive.
Mr Erdogan has strongly defended the incursion, threatening to send some of the 3.6 million Syrian refugees it hosts to Europe if the Turkish offensive is described as an occupation.