BEIRUT - The Islamic State group killed more than 50 people in an attack on two government-held villages in central Syria’s Hama province on Thursday, a monitor said.

The militants executed some of those killed in the assault, which comes as IS loses territory elsewhere in Syria and in neighbouring Iraq.

The Britain-based Syrian Observatory for Human Rights said the attack on the villages of Aqareb and Al-Mabujeh killed at least 15 civilians and 27 pro-government fighters. It said another 10 bodies were yet to be identified as government fighters or local residents.

IS also lost 15 fighters in the dawn attack on the two villages in the east of the province, the monitor said.

Observatory director Rami Abdel Rahman said at least three of the civilians were killed execution style with knives, a man and his two children. It was unclear if others had also been killed the same way or died in fighting.

Syria’s state news agency also reported 52 people had been killed in the IS assault, though it described the attack as against Aqareb only. It said IS fighters had mutilated the bodies of villagers and looted their homes, and said that 15 of the dead were children.

The Observatory said IS had seized control of Aqareb and part of Al-Mabujeh in the attack, which began with heavy shelling on a nearby regime checkpoint. “Despite the arrival of reinforcements, government forces have been unable to repel the attack so far,” Abdel Rahman told AFP. He said the fighting was continuing and had spread to the outskirts of nearby villages.

IS has attacked Al-Mabujeh before with devastating effect.

In March 2015, it executed at least 37 civilians in the village, whose population includes Sunni Muslims as well as those from the Ismaili sect and the Alawite community to which President Bashar al-Assad belongs.

During the same assault the group kidnapped at least 50 civilians, half of them women.

Control of central Hama province is divided between Syria’s government, rebel forces and IS, which is present mostly in the east of the area.

The attack comes as IS faces pressure in the north of the country, where an alliance of Kurdish and Arab fighters is preparing an assault on its bastion Raqa city. The militant group has also lost most of the Iraqi second city of Mosul, which it captured in 2014.

Meanwhile, US-led coalition aircraft Thursday struck a pro-regime convoy apparently transporting Shia militiamen in Syria as it headed toward a remote coalition garrison near the Jordanian border, US defence officials said.

While officials stressed the defensive strike did not signal deepening US involvement in Syria’s civil war, it nonetheless raises questions about the ongoing feasibility for the coalition to maintain its singular focus on the Islamic State group.

In a statement, the coalition said the strike had occurred “well inside” an established de-confliction zone northwest of the At-Tanf garrison, where British and US commandos have been training and advising local forces fighting IS.

“A convoy going down the road didn’t respond to numerous ways for it to be warned off from getting too close to coalition forces in At-Tanf,” a US defence official told AFP on condition of anonymity.

“Then there was finally a strike against the lead portion of that movement.”

A second defence official told AFP the forces in the convoy appeared to have been Shia militia.

Attempts to stop the convoy included a call to the Russians - who are working with the Syrian regime - then a “show of force” in the skies above the vehicles, followed by warning shots.

The first official said the convoy was “significant” in size, but only the lead vehicles were hit.

Coalition officials said Russian forces had apparently unsuccessfully tried to dissuade the pro-regime movement south.

Describing the hours-long event as an “escalation-of-force situation,” the official said it did not signal a strategic shift for the coalition, which remains focused on fighting IS group.

Yehya al-Aridi, a spokesman for the Syrian opposition High Negotiations Committee in Geneva, praised the strike.

“We welcome robust action against the foreign forces who have turned Syria into a killing field,” he said.

“Iran and its militias have kept (President Bashar-al) Assad in power. They cannot be allowed to wage war on our soil with impunity.”

America has been militarily involved in Syria since 2014 but has for the most part avoided engaging directly in the country’s civil war.

The biggest exception to this was a US cruise missile attack on a Syrian airbase last month in response to a suspected chemical attack by the regime.

At-Tanf has been the target of repeated attacks in recent months.

Last month, US-led allied forces and Syrian rebels thwarted a significant IS attack on the base.

And in June last year, Russian warplanes bombed the outpost, reportedly just one day after British special forces had pulled out.