BAGHDAD/DAMASCUS - An Islamic State group rocket expert believed to have been involved in an attack that killed a US Marine has died in a drone strike in Iraq, a spokesman said Sunday.

Staff Sergeant Louis Cardin was killed last month by an IS rocket attack that also wounded eight Marines at an artillery position in the Makhmur area of northern Iraq. ‘Several hours ago, we killed an ISIL (IS) member believed responsible for the rocket attack that resulted in the death of Sergeant Cardin,’ Colonel Steve Warren, the spokesman for the US-led operation against the jihadists, told journalists in Baghdad.

Jasim Khadijah ‘was an ISIL member and former Iraqi officer,’ he said. He was ‘a rocket expert, apparently he controlled those attacks,’ Warren said, adding that the strike also killed five other IS fighters and destroyed a drone and two vehicles.

IS overran large parts of Iraq in 2014, but the country's forces have since regained significant ground with the backing of US-led air strikes and training. US President Barack Obama repeatedly pledged that there would be no ‘boots on the ground’ to fight IS, but has deployed special forces to Iraq who are carrying out raids targeting the jihadists. An American special operations soldier was killed last October during a joint raid with Kurdish forces against IS in Hawijah, a northern Iraqi town. Moreover, the anti-Islamic State coalition conducting airstrikes in Iraq and Syria has killed the IS militant believed responsible for an attack on U.S. troops in northern Iraq last month that left a Marine dead, it said on Sunday.

Militant Jasim Khadijah, a former Iraqi officer not considered a high-value target, was killed by a drone strike overnight in northern Iraq, coalition spokesman US Army Col. Steve Warren told reporters in Baghdad.

‘We have information (that) he was a rocket expert, he controlled these attacks,’ said Warren, referring to the shelling of a base used by U.S. troops near the town of Makhmour, located between Mosul and Kirkuk.

That attack killed Marine Staff Sergeant Louis Cardin and wounded eight others, all part of a company-sized detachment of less than 200 troops. They provide force protection fire to Iraqi army troops, who are making slow progress in a campaign to clear areas around Mosul, an IS stronghold. Cardin's was the second combat death of an American service member in Iraq since the start of the campaign to fight the militant group in 2014. Warren said five other Islamic State fighters were killed in the air strike. In the meanwhile, Syrian troops on Sunday seized the key Islamic State group bastion of Al-Qaryatain, dealing the jihadists a new blow in the country's centre a week after expelling them from Palmyra, state television said.

The Syrian Observatory for Human Rights monitoring group however said fighting was still raging in the east and southeast of the town, which is located in the desert in Homs province. ‘The army with backing from supporting forces (pro-regime militia) brings back complete security and stability to the town of Al-Qaryatain, after crushing Daesh terrorists' last remaining positions there,’ state television said, using an Arabic acronym for IS.

But the Britain-based Observatory said the army was still fighting the jihadists in about half the town. ‘Clashes are still ongoing in the east and southeast of the town,’ it said. The advance came after the Russian-backed Syrian army dealt IS a major blow on March 27 by seizing the ancient city of Palmyra, known as the ‘Pearl of the desert’, from the jihadists.

Al-Qaryatain is located some 120 kilometres (75 miles) southwest of Palmyra. Its recapture will allow the army to secure its grip over the ancient city, where jihadists destroyed ancient temples and executed 280 people during their 10-month rule. Once Al-Qaryatain returns to government control, ‘of the whole of Homs province, IS will only hold its bastion in Sukhna’ northeast of Palmyra, Observatory chief Rami Abdel Rahman said.

‘The recapture of Al-Qaryatain will also allow the army to reclaim the whole of the Syrian desert’ spreading all the way south to the Iraqi border, Abdel Rahman added. A ceasefire brokered by the United States and Russia but which does not apply to the fight against jihadists has enabled the Syrian army to focus on efforts to crush IS.