A Syrian military source said on Saturday that government forces had repelled an attack by Islamic State militants on an air base in the eastern province of Deir al-Zor, one of the last remaining government stronghold in eastern Syria.
The Britain-based Syrian Observatory for Human Rights said Islamic State fighters broke into the Deir al-Zor (DeirEzzor) air base at dawn on Saturday but were forced to retreat. It said 119 fighters on both sides were killed.
A Syrian security source, when asked about the breach, said: “The terrorists have been unable to control the air base.”
The al Qaeda offshoot Islamic State has been gradually consolidating control of the oil-producing Deir al-Zor province this year. President Bashar al-Assad's forces have held on to the local military air base and parts of the provincial capital.
The Observatory said 51 of Assad's forces and 68 members of Islamic State had been killed in the three-day offensive.
"Elements of the Islamic State also pulled out of a mountain overlooking Deir al-Zor due to intense shelling," the Observatory said.
State media said on Saturday that the army had killed "a number of terrorists" in al Jufra, an area close to the airport.
Islamic State has been under pressure from U.S. air strikes in Syria since September, but that has not stopped it from launching attacks on Assad's forces and other targets to expel government forces and rival rebels.
The Twitter account of the U.S. embassy in Syria said late on Friday that a U.S. air strike in Deir al-Zor had hit Islamic State targets: three vehicles, an excavator and a training camp.
It was unclear whether the attacks took place near the base.
Deir al-Zor borders territories in Iraq are also controlled by Islamic State. The province's oilfields are a major source of revenue for the group.