An air strike believed to have been carried out by the U.S.-led coalition killed four Syrian military personnel in Deir al Zor province, which is mostly held by Daesh, a monitoring group said on Monday, in what would be the first time coalition warplanes had hit Syrian government forces.A source close to the Syrian government confirmed the strike and said there had been casualties and vehicles destroyed.Syria Foreign Ministry said that four jets from U.S.-led coalition targeted Syrian army camp with nine missiles, killing three soldiers, wounding 13 on Sunday, Reuters reported.Meanwhile, the US-led coalition denied the allegations saying its planes carried out air strikes that killed at least three Syrian regime troops. "We've seen those Syrian reports but we did not conduct any strikes in that part of Deir Ezzor yesterday. So we see no evidence," said Colonel Steve Warren, spokesman for the coalition.He said the coalition's only strikes in Deir Ezzor on Sunday were some 55 kilometres (34 miles) southeast of the area where the troops were allegedly killed, near the town of Ayyash."We struck 55 km away from the area that the Syrians say was struck. That was the only area in Deir Ezzor we struck yesterday," he told AFP."There were no human beings in the area that we struck yesterday, all we struck was a wellhead," he added.The Syrian Observatory for Human Rights said the strike hit part of the Saeqa military camp near the town of Ayyash in western Deir al Zor province and wounded 13 military personnel in the first such incident since the coalition began its bombing campaign against Daesh in Syria.The strike had hit some time in the last 24 hours, it said.The U.S.-led force's campaign is against Daesh, which controls most of Deir al Zor, including its capital, and has regularly targeted the group in the eastern Syrian province.In Deir al Zor city, another air strike believed to be carried out by the coalition overnight killed a woman and two of her children, the Observatory said.Deir al Zor province links Daesh's de facto capital in Raqqa with territory controlled by the group in Iraq, and its oilfields are a major source of revenue for the group.