US-led coalition jets bombed a Syrian army position at Jebel Tharda near Deir al-Zor airport on Saturday, killing dozens of Syrian soldiers, Russia and a war monitoring group said, paving the way for Islamic State fighters to overun it.
Syria’s army general command said in a statement that the air strike was “conclusive evidence” of U.S. support for Islamic State, noting that the strike was “dangerous and blatant aggression”.
Islamic State said in a statement on its Amaq news channel that it had gained “complete control” over Jebel Tharda.
The defence ministry in Russia, which has been aiding Syria’s President Bashar al-Assad in the five-year-old civil war, said U.S. jets had killed more than 60 Syrian soldiers in four air strikes and that a fierce battle was now taking place near the airport.
The Syrian Observatory for Human Rights, a Britain-based monitoring group with contacts across the country, cited a military source at Deir al-Zor airport as saying that at least 80 Syrian soldiers had been killed in the strike.
Russia’s Defence Ministry said that if the coalition bombing was a mistake, it was evidence of Washington’s “stubborn refusal” to coordinate its actions with Russia’s government.
The U.S.-led coalition has been conducting air strikes against Islamic State since September 2014 and is also supporting rebels against Assad elsewhere in Syria.
In December, Damascus accused U.S. coalition warplanes of striking an army camp near Deir al-Zor, but Washington said it was done by Russian jets.
The Observatory said that Russian jets had been conducting bombing in the area at the same time, that Islamic State fighters took control of army positions on Jebel Tharda after the air strike and that clashes between them had followed.
A strike list issued by the U.S. on Saturday said it had carried out a strike at Deir al-Zor against five Islamic State supply routes, as well as strikes near Raqqa and elsewhere in Syria.
The U.S. military did not immediately respond to requests for comment.
Syria’s army controls Deir al-Zor airport and parts of the city which are otherwise entirely surrounded by territory held by Islamic State.
The United States and Russia agreed a deal on Syria last week, involving a ceasefire which came into effect on Monday, aid deliveries to besieged areas and eventual joint targeting of militant jihadist groups if the truce works out.
Syria’s war between Assad and rebels seeking to topple him has drawn in regional and global powers and allowed militant jihadist groups including Islamic State to gain territory and inspire attacks.