BEIRUT • Turkish forces and their allies attacked Syrian government troops in northeastern Syria on Thursday, killing some of them, and they also clashed with Kurdish-led fighters, the state news agency in Damascus and a war monitoring group said.

The fighting underscored the risks of violence as multiple and often opposing armed forces jostle for new positions in the tight quarters of the northeastern border zone. Most worrisome has been the prospect of a collision between forces of the Syrian government’ and those backed by Turkey, which include Syrian rebel fighters and Islamic extremists opposed to President Bashar Assad.

All sides have said they are abiding by a cease-fire as they implement a Russian-Turkish agreement that divides up the border region. But frictions could undermine the effort for a resolution on the border, which U.S. forces were abruptly ordered to leave earlier this month, allowing Turkey to launch its invasion against Kurdish fighters.

Syria’s state-run SANA news agency said Turkish troops attacked Syrian army positions outside Tal Tamr.