Al-Qaeda-linked jihadist Mokhtar Belmokhtar, who allegedly masterminded the siege of an Algerian gas plant in which 38 hostages died, has been killed in a US air strike, Libya's government said.

"American jets conducted an operation which resulted in the deaths of Mokhtar Belmokhtar and a group of Libyans belonging to a terrorist organisation in eastern Libya," the internationally recognised government said on Facebook.

The Pentagon said Belmokhtar had been the target but did not confirm the Islamist's death, which has often been reported in the past.

US Air Force Secretary Deborah Lee James said "precision weapons" were used in the raid.

She also did not comment on Belmokhtar's reported death, saying: "The actual impact of that raid is still being assessed."

Pentagon spokesman, Colonel Steve Warren, said two F-15 Strike Eagle fighter jets armed with 500-pound bombs took part in the attack in eastern Libya and were escorted by observation drones.

French President Francois Hollande, speaking on a visit to Algeria, said there was a "very high probability that Belmokhtar was killed," citing a convergence of information.

Mauritanian jihadist expert Isselmou Ould Salihi said that if confirmed Belmokhtar's death would "that a page in the history of jihadism in the Sahara has been turned".

Hatem el-Ouraybi, spokesman for the recognised government, told AFP "coordination with the US will continue in fighting these terrorist groups."

The strike came as part of "the international support that we have always asked for in order to fight terrorist groups in Libya," he said.

Belmokhtar, nicknamed variously as "The Uncatchable", "Mr Marlboro" and "The One-Eyed", was leader of the North African Al-Murabitoun militant group and a former chief of Al-Qaeda in the Islamic Maghreb (AQIM).

He allegedly masterminded the 2013 siege of an Algerian gas plant in which 38 hostages, mostly Westerners, were killed.

- 'First strike since 2011' -

Washington has previously used drones against targets in North Africa, but the New York Times said this was the first US air strike of any kind in Libya since Moamer Kadhafi's regime fell in 2011.

The last US operation in Libya was in 2014, when special forces captured Ahmed Abu Khattala, an alleged organiser of the attack against the US consulate in Benghazi in 2012 that killed ambassador Chris Stevens and three other Americans.

Libya said the operation came "after consultation with the Libyan transitional government" based in the east.

Prime Minister Abdullah al-Thani called it "part of international aid that has long been sought in the fight against terrorism".

Lana news agency cited a government official as saying the strikes targeted a farm south of Ajdabiya, some 160 kilometres (100 miles) west of Benghazi, as Belmokhtar met leaders from other extremist groups including Ansar al-Sharia, listed by Washington as a "terrorist" organisation.

Belmokhtar was previously thought to have been killed in Mali, but security sources said last year he had moved to Libya.

Born in 1972 in Algeria, he said in a rare 2007 interview he had been fascinated with the exploits of the mujahedeen combating the Soviet invaders of Afghanistan, and joined them in 1991 when he was barely 19.

It was in Afghanistan that he said he lost his eye to shrapnel and where he had his first contact with Al-Qaeda.

He returned to Algeria in 1993, eventually joining the group that became AQIM.

- 'Continued divisive activities' -

But he was pushed out as one of AQIM's top two leaders in northern Mali for what one regional security official said were his "continued divisive activities despite several warnings".

A Malian official cited AQIM as saying that Belmokhtar, whose nickname "Mr Marlboro" came from his reputation as a cigarette smuggling baron, had been "dismissed for straying from the right path".

A scathing Al-Qaeda letter criticising him hit the headlines in 2013 in the wake of French armed intervention in Mali.

Belmokhtar founded his Al-Qaeda breakaway group "Signatories in Blood" in 2012, later merging it with MUJAO, one of the jihadist groups that seized northern Mali in early 2012, to form Al-Murabitoun.

Along with the Algerian siege, Belmokhtar also claimed a May 2013 double suicide bombing in Niger that killed 20 people.

Al-Murabitoun last month said it had pledged allegiance to the Islamic State group, but Belmokhtar immediately distanced himself from the declaration. He vowed backing for Al-Qaeda in what was interpreted as evidence of a serious power struggle.

Libya has descended into chaos since a NATO-backed revolt unseated longtime dictator Kadhafi. It has rival governments and parliaments, with powerful militias battling for influence and a share of its oil wealth.

Jihadist groups have exploited the lawlessness, which has also prompted a huge influx of migrants trying to make the dangerous Mediterranean crossing to Europe, with hundreds dying in shipwrecks and the EU straining to respond.

burs/dv