An Islamist militant, blamed for masterminding an Algerian gas field attack and running smuggling routes across North Africa, has reportedly been killed in a US air strike inside Libya.

Algerian Mokhtar Belmokhtar was a major figure in insurgencies across North Africa and the Sahel and had earned the nickname the "Uncatchable" from the French military.

The US military confirmed Belmokhtar had been targeted in the air strike on Saturday night, but did not say if he had been killed. 

Pentagon spokesman Colonel Steve Warren said: "We are continuing to assess the results of the operation and will provide more details as appropriate."

The Pentagon said yesterday it had carried out a strike against an al-Qaeda-affiliated target in Libya, but did not elaborate.

Following the initial US statement, Libya's recognised government said: "The Libyan government in the east of Libya confirms that US fighter jets conducted air strikes last night in a mission which resulted in the death of the terrorist Belmokhtar."

Belmokhtar has been reported killed several times, including in 2013 when he was believed to have died in fighting in Mali.

He has earned a reputation as one of the most elusive jihadi leaders in the region.

If confirmed, the death of Belmokhtar - who was blamed for orchestrating the 2013 attack on Algeria's In Amenas gas field in which 40 oil workers died, and for several foreign kidnappings - would be a major strike against al-Qaeda-linked groups in the region.

Once associated with al-Qaeda in the Islamic Maghreb's Algerian leadership, Belmokhtar broke from the group but remained tied to al-Qaeda's central leadership even after forming his own group.