US troops in Syria came under fire from Turkish positions: Pentagon

US troops in northern Syria came under artillery fire from Turkish positions on Friday but none were wounded, the Pentagon said, an incident that highlights the risks to US troops as Turkey wages an offensive against US-allied Kurdish militia.

"The explosion occurred within a few hundred meters of a location outside the Security Mechanism zone and in an area known by the Turks to have US forces present," Navy Captain Brook DeWalt, a Pentagon spokesman, said in a statement.

DeWalt said that all US troops were accounted for after the incident near Kobane, Syria late on Friday.

US troops have not withdrawn from Kobane, he said.

Turkey's Defence Ministry said it had taken all measures to ensure that no US base was damaged while it responded to harassment fire that originated near a US base close to Kobane.

"The firing was ceased as a result of the issue being relayed to us by the US," the ministry said in a statement.

US forces have had a successful partnership with Kurdish YPG militia in Syria to oust the Islamic State group.

Syrian rebel fighters drive a tank through a field near Tal Abyad, Syria, Oct 11, 2019. REUTERS

"The US demands that Turkey avoid actions that could result in immediate defensive action," DeWalt said.

Turkey's Defence Ministry said there was no firing on the US observation post, adding that it fired in response to an attack on its military posts south of the town of Suruc, across the border from Kobane.

The Chairman of the Joint Chiefs of Staff General Mark Milley told reporters at the Pentagon earlier on Friday that Turkey had been told of US positions in Syria, "down to explicit grid coordinate detail."

Top Pentagon officials stressed the need for Turkey to avoid doing anything to endanger US forces inside Syria, which numbered about 1,000 before the incursion. Although US troops had no intention of firing on Turkey, a NATO ally, the Pentagon noted they had the right to defend themselves.

"Everyone is fully aware that we are the United States military. We retain the right of self-defence," Milley said.

Turkey's offensive began days after US President Donald Trump spoke by phone on Sunday with Turkish President Tayyip Erdogan and ordered US troops to be moved out of the way.

US military officials denied accusations by lawmakers and policy analysts that the Trump administration had abandoned its allies. Turkey says its aim is to defeat the Kurdish YPG militia, which it sees as an enemy for its links to insurgents in Turkey.