A car bomb explosion near a gas plant in Syria's Homs province on Monday killed nine people including four soldiers, a monitoring group said, updating an earlier toll.

The jihadist Islamic State (IS) group claimed responsibility for the attack and said the two bombers were killed.

State news agency SANA confirmed the attack but said that troops had captured the bombers.

"Five employees and four regime troops guarding the Firqlos gas plant were killed in a car bomb blast near the facility in the east of Homs province," said the Syrian Observatory for Human Rights.

The explosion also wounded 15 people.

It took place "at the start of the working day", the Britain-based group added.

SANA, quoting a military source, said "guards captured the two terrorists who detonated the pick-up truck at the entrance to the plant while they were trying to flee."

IS said the two men, both Moroccan, had died.

The jihadists have targeted oil and gas facilities in Iraq and Syria as the group seeks funds for its fight to seize territory for a self-proclaimed Islamic "caliphate".

In November, Syrian troops backed by pro-regime militiamen recaptured the Shaer gas field in central Homs province, a week after IS fighters overran parts of the complex.

IS killed some 350 regime troops and loyalist militiamen, as well as gas plant workers, during its attempt to take Shaer.

Elsewhere in Syria, the Observatory said the number of IS members killed fighting Kurdish forces in the flashpoint town of Kobane on Sunday had risen to 18.

Another two IS suicide attackers also died, as did 10 members of the Kurdish People's Protection Units (YPG), it said.

The jihadists launched a major offensive in mid-September to try to capture Kobane, and at one point controlled more than half the town, known in Arabic as Ain al-Arab.

But backed by US-lead coalition airstrikes on IS positions, Kurdish forces have regained control of several neighbourhoods.

Coalition aircraft struck IS targets in Kobane on Sunday night, the Observatory said, and a Pentagon statement said 10 strikes hit the area on Monday.

More than 1,000 people are reported to have been killed in the battle for the town, most of them jihadists.