A US airstrike inside Libya over the weekend killed the so-called "The Uncatchable," a veteran Islamist militant blamed for the attack on an Algerian gas field that killed 40 people, a Libyan government source has announced.

Mokhtar Belmokhtar, whose monicker was given by the French military, was an Algerian militant who had major roles in insurgencies across North Africa and the Saharan border region, according to a Reuters report.

The US military confirmed Belmokhtar was indeed the target of the airstrike launched on Saturday night but gave no confirmation if he was killed.

The operation's results are still being assessed, spokesperson Colonel Steve Warren said in a statement.

The veteran militant's death was hailed by Libya's internationally recognized government, which said he was killed in the company of other militant leaders whose names were not disclosed.

No other details were given about the area of the airstrike, but sources from the Libyan military said the attack on a farmhouse in Ajdabiya city near Benghazi killed seven members of the Ansar al Sharia militant group who were convening there.

However, this is not the first time that the elusive jihadi has been declared as dead. He reportedly died in 2013 during the fighting in Mali, among other incidents.

If his death is indeed true, it would be a major blow against al Qaeda-tied groups in the region. Previously associated with al-Qaeda in the Islamic Maghreb's Algerian leadership, the one-eyed veteran separated from the group but remained linked to al-Qaeda's central leadership, even after forming his own group called "Those who sign in Blood."

Belmokhtar allegedly was the brains behind the attack on Algeria's In Amenas gas field. He was also blamed for several abductions of foreigners in North Africa.

The jihadist was a veteran of Afghanistan and Algeria's own Islamist war in the 1990s.