Media playback is unsupported on your device Media caption Mokhtar Belmokhtar had a reputation for being elusive, as Mike Woodridge reports

A top Islamist militant who ordered a deadly attack on an Algerian gas plant two years ago has been killed in a US air strike in Libya, officials say.

Mokhtar Belmokhtar was killed in the eastern city of Ajdabiya, a statement from Libya's government said.

The US says Belmokhtar was targeted and the strike was successful, but it is assessing the operation's results and would give details "as appropriate".

Mokhtar Belmokhtar's death has been reported many times in the past.

Notoriety

Born in Algeria, Belmokhtar was a former senior figure in al-Qaeda in the Islamic Maghreb (AQIM), but left to form his own militia.

He gained notoriety with the attack on the In Amenas gas plant in Algeria in 2013, when about 800 people were taken hostage and 40 killed, most of them foreigners, including six Britons and three Americans.

The US has filed terror charges against him and officials said they believed he remained a threat to Western interests.

"Belmokhtar has a long history of leading terrorist activities as a member of AQIM, is the operational leader of the al-Qaeda-associated al-Murabitoun organisation in north-west Africa, and maintains his personal allegiance to al-Qaeda," said Pentagon spokesman Col Steve Warren.

Analysis: Jonathan Marcus, BBC Diplomatic Correspondent

Dead, or maybe still alive, either way the fact that the US is still hunting Mokhtar Belmokhtar illustrates the breadth and tenacity of the US counter-terrorism effort.

While the focus is now very much on combating Islamic State in Iraq and Syria, the US struggle against al-Qaeda franchises continues both in the Middle East (Libya in this case) and to a growing extent in sub-Saharan Africa too.

Belmokhtar masterminded the attack on the Amenas gas plant in Algeria in 2013 in which 40 people were killed, including three Americans.

He was targeted not in a drone strike but an attack launched by two F-15 aircraft.

Libya looks set to be an area of renewed concern for the Americans, the instability prompted by the removal of Muammar Gaddafi in 2011 providing a rich vein of ungoverned space in which various Islamist militants, including Islamic State are establishing a significant presence.

How do you verify a militant's death?

The Libyan government said the strike came after consultation with the US. Their statement said it resulted in the death of the "terrorist Belmokhtar".

Libya has been in chaos since the ousting of Muammar Gaddafi in 2011.

Its internationally recognised parliament is operating in exile in the eastern port of Tobruk.

A rival parliament, the Islamist-dominated General National Congress, is nearly 1,000km (620 miles) to the west in Tripoli.

Rival militia have been battling to fill the power vacuum, with Islamic State militants battling other Islamists in the east.

Mokhtar Belmokhtar

Image copyright SITE INTEL GROUP Image caption Belmokhtar has been seen speaking before an operation in Niger