Syrian government warplanes, in repelling an attack on a key military air base in eastern Syria by Islamic State fighters, carried out at least eight airstrikes on Sunday against the militants, activists said.
"Troops and pro-regime militia stopped the attack that Islamic State launched on the Deir Ezzor military airport," the Britain-based Syrian Observatory for Human Rights said, adding that both sides suffered heavy losses in the fighting.
The Islamic State group launched its assault on the airfield just outside the city of Deir al-Zour last week, touching off fighting that the human rights activists said has killed more than 150 people on both sides since Wednesday.
The activists said Islamic State fighters succeeded in storming part of the base. On Saturday, the Syrian military launched a counterattack, including heavy air raids, to push the militants back.
Scattered clashes on the ground continued Sunday with fighting on several fronts around the base, activists said.
The Observatory said the Islamic fighters had withdrawn to the edges of the air base, a day after managing to seize a southeastern part of the complex.
The Deir Ezzor air base is a key regime outpost from which warplanes and helicopters mount raids on jihadist positions in several areas of the war-wracked country.
For the Islamic State group, seizing control of the base would eliminate the last significant government presence in the area and provide a major morale and propaganda boost.
Also Sunday, Iraqi security sources, speaking on condition of anonymity, said Islamic State fighters executed 12 Shi'ite militiamen in the town of Tal al-Thahab on Saturday.
Iraqi security forces and Shi’ite militia fighters had launched an attack against Islamic State fighters for the town, near Balad, 80 kilometers (50 miles) north of Baghdad, on Friday.
They managed to force the Islamic militants from the town, but hours later the Islamic fighters returned, encircling the town and trapping dozens of Iraqi troops and Shi’ite militiamen.
An army intelligence officer said army helicopters and supporting troops reached the area to help dirve off the Islamic State fighters, but he confirmed to Reuters that “12 volunteer fighters were executed on Saturday by terrorists.”
Balad's mayor, Amir Abdul Hadi, confirmed that some of the Shi'ite militiamen were executed by Islamic State fighters near Balad and others were missing after Friday's battle, but said he did not have details. Officials said 10 militiamen were missing.
Balad houses a shrine to a revered Shi'ite imam and is one of several towns north of Baghdad that has seen heavy fighting between Islamic State fighters and Iraqi security forces and pro-government Shi'ite militia.
Security and local officials said Sunday more Shi'ite militia fighters were gathering in Balad to try to drive out Islamic State militants from areas surrounding the town.
Also, at least eight people were killed over night In the town of Tarmiya, between Balad and Baghdad, when militants detonated a car bomb overnight at a security checkpoint before attacking with guns, security and medical officials said on Sunday.
A police officer said the assault started with a car bomber attacking the police station and was then followed with an assault by armed militants.
Five police and three civilians were killed, security and medical sources told Reuters. The Associated Press said at least 11 people were wounded.
No group immediately claimed responsibility for the attack.
Material for this report came from Reuters, AFP and AP.