The Turkish offensive against Syrian Kurdish fighters in northeastern Syria entered its third day on Friday.
Explosions were seen sending plumes of smoked into the sky in the Syrian border town of Tal Abyad.
The Turkish air and ground assault was launched three days after US President Donald Trump opened the way by pulling American troops from their positions near the border alongside their Kurdish allies.
Turkish Foreign Minister Mevlut Cavusoglu said the military intends to move 30 kilometres (19 miles) into northern Syria and that its operation will last until all "terrorists are neutralised."
Meanwhile on Thursday, Trump told reporters at the White House that the US has only two choices: Hit Ankara hard with financial sanctions or send in US troops to stop the fighting between Turkish and Kurdish forces.
Trump said Turkey knows he does not support the invasion.
But he also said he doesn't think the American people want to send troops there but said he hopes the US can mediate.