File picture shows firefighters trying to put out the fire in an oil tank in the port of Es Sider, in Ras Lanuf, Libya.

Decisive military action is needed to halt the spread of Islamic State of Iraq and Syria (ISIS) in Libya, the top U.S. military officer said on Friday, saying the group wanted to use the north African nation as a platform to coordinate activity across the continent.

“Unchecked, I am concerned about the spread of ISIL in Libya … So I believe that military leaders owe the secretary of defense and the president a way ahead for dealing with the expansion of ISIL in Libya,” said chairman of the Joint Chiefs of Staff General Joseph Dunford, using an acronym for ISIS.

Speaking to a small group of reporters during a trip to Paris, he added: “You want to take decisive military action to check ISIL’s expansion and at the same time you want to do it such a way that’s supportive of a long-term political process.”

Meanwhile, firefighters on Friday battled a blaze at an oil facility in northern Libya for a second day, an official said, after an assault by militants aiming to seize export terminals.

Libya’s internationally-recognized government, meanwhile, called for Western air strikes to repel the militants.

“Four storage tanks together containing around two million barrels of crude oil are on fire,” said a security official in the Ras Lanouf region along Libya’s northern coast.

The blaze in one of the tanks is beyond control “and we expect it to collapse at any moment,” he said. “We are now working on putting out the fires in the other three tanks.”

“The disaster exceeds our capacities,” added the official, asking not to be named.

Fighting broke out at dawn on Thursday in Ras Lanouf, the National Oil Corporation (NOC) said.

It said storage tanks filled with crude had caught fire, causing clouds of dense smoke.

It called the situation “catastrophic for the environment” and said that nearby high-voltage power lines and electrical towers had also been downed.

State news agency LANA said ISIS group militants were behind the attack and that the storage tanks belonged to Harouge Oil Operations.

The company has 13 storage tanks with a combined capacity of 6.5 million barrels at its site, nine kilometers (six miles) from Ras Lanouf port.

An NOC official told AFP a committee has been formed to evaluate the damage.

The attack came two days after a national unity government was formed under a U.N.-brokered deal aimed at ending political divisions that have seen Libya torn between rival administrations.

A spokesman for Libya’s recognized government in the east told AFP it was requesting a “limited intervention by the international community to “protect oil fields from ISIS attacks.”

Hatem el-Ouraybi said the government wanted “air strikes against ISIS positions” in Libya.

The government has previously called for an air campaign against ISIS, like in Iraq and Syria, but world powers are first waiting for rival sides to endorse the unity government.

ISIS has in recent weeks launched repeated attacks from its stronghold in the city of Sirte on facilities in the “oil crescent” along the country’s northern coast.

Libya sits atop estimated oil reserves of 48 billion barrels, the largest in Africa.

But output has slumped since the North African country’s longtime leader Muammar Qaddafi was ousted and slain in a 2011 revolution, tipping the country into insecurity and political chaos.

Related articles across the web

• Libya: Reconciliation At Last? - OpEd
• GOP debate: Should US deal with dictators?
• Adafruit's comic reading list: The Arab of the Future: A Childhood in the Middle East by Riad Sattouf #adafruitcomics @riadsattouf
• Libya parliament chief throws U.N. deal into doubt
• Dictatorships, double standards and Ted Cruz: Bloomberg View
• World News Briefs -- December 16, 2015
• Choosing Not to Choose: Obama's Dithering on Syria
• Libya's General Heftar pushes for End to Arms Ebargo
• The most important moment at last night's GOP debate
• A chance of peace