Islamic State militants launched attacks near oil facilities in northern Libya on Monday but were pushed back, an army official has said.

The jihadis carried out a suicide car bomb attack on a military checkpoint at the entrance to the town of al-Sidra, killing two soldiers, said a colonel in the army loyal to the internationally recognised government.

“We were attacked by a convoy of a dozen vehicles belonging to Isis,” Bashir Boudhfira said. “They then launched an attack on the town of Ras Lanouf via the south but did not manage to enter.”

For several weeks Isis has been trying to push east from the coastal city of Sirte under its control to reach Libya’s “oil crescent” where key oil terminals such as al-Sidra and Ras Lanouf are based.

A Libyan oil official said a 420,000-barrel oil tank in Ras Lanouf caught fire during the clashes.

Isis announced on Twitter that its fighters had led an “attack on the al-Sidra area followed by violent clashes with the enemies of God”.

The group has taken advantage of chaos in Libya since the 2011 revolt that ousted and killed longtime dictator Muammar Gaddafi to extend its influence there. Monday’s attack is the first of its kind since Isis seized Gaddafi’s home town of Sirte in June 2015.

The group said the attack came after it took control of Ben Jawad town, 90 miles (150km) east of Sirte. No official or army source could confirm this.

Oil is Libya’s main natural resource, with a pre-revolt output capacity of about 1.6m barrels per day, accounting for more than 95% of exports and 75% of the budget.

But unrest has forced a major slump in production. The country sits on reserves estimated at 48bn barrels of oil, the largest in Africa.

Libya has had rival administrations since August 2014, when an Islamist-backed militia alliance overran Tripoli, forcing the government to take refuge in the east.

The UN is pressing both sides to accept a power-sharing agreement it hopes will help reverse gains made by Isis.

On 17 December, under UN guidance, envoys from both sides and a number of independent political figures signed a deal for a unity government. It calls for a 17-member government, led by businessman Fayez el-Sarraj as premier, based in Tripoli.