The U.S. military has said it stopped an air raid against Islamic State (IS) militants in eastern Syria after Russian officials said it may have bombed Syrian army troops.
The Syrian Observatory for Human Rights said at least 80 Syrian soldiers had been killed in the bombing, RFE/RL reports.
Syrian media did not report how many soldiers had been killed and injured.
But the London-based monitoring group said it was unable to say who carried out the air strikes. It said Russian jets had been carrying out bombing raids in the area at the same time.
The Syrian troops had been involved in a fierce fight with IS militants at Jebel Tharda, which is near the Deir al-Zor air base where the attack on the Syrian forces occurred.
The military added that the aerial attack had allowed Islamic State (IS) militants to advance on a hill that overlooks the Syrian Army's air base.
The statement called the air strikes 'a serious and blatant attack on Syria and its military' and said they represent 'firm proof of the U.S. support of [IS] and other terrorist groups.'
The U.S.-led coalition began its bombing campaign against Islamist fighters in Syria and Iraq two years ago.
Russia and the United States brokered a cease-fire on September 12, but both sides have criticized the other for not following through on the agreements made in the cease-fire, including allowing humanitarian aid to people besieged in the city of Aleppo and other nearby areas.
At least 250,000 people are estimated to have been killed since the start of Syria's civil war in 2011. Millions of others have fled their homes.
As reported earlier by 1492news.com, U.S.-led coalition air strikes reportedly killed dozens of Syrian soldiers.