The Libyan government said Monday that US airstrikes over the weekend had killed the "uncatchable" Mokhtar Belmokhtar, the al Qaeda-linked militant leader in Libya charged with leading the attack on a gas plant in Algeria in 2013 that killed at least 35 hostages, including three Americans.

An Islamist with ties to Libyan militants, however, said the airstrikes missed Belmokhtar, instead killing four members of a Libyan extremist group the U.S. has linked to the September 2012 attack on the U.S. Consulate in Benghazi that killed Ambassador Chris Stevens and three other Americans.

Also known as "Belaouer the One Eyed," "The Uncatchable," and "Mister Marlboro" — the last name a play on the fact he's accused of smuggling contraband cigarettes through the Sahara and the Sahel — Belmokhtar built a bridge between al Qaeda's regional branch in Algeria, AQIM, and the underworld there, according to intelligence officials.

They say he created a system where various blends of outlaws now support each other and enroll local youth. He's also been linked to terror attacks and the lucrative kidnapping of foreigners in the region.

Belmokhtar, who is originally from Algeria, had been involved in the jihadi movement since the Soviet invasion of Afghanistan. He claimed to have traveled there as a teenager in the mid-1980s and fought alongside the Taliban and al Qaeda against the USSR, gaining a lifelong devotion to the Islamist struggle but reportedly losing one of his eyes. He went on to fight against Algeria's government during the 1990s and later joined al Qaeda.

Belmokhtar left AQIM in late 2012 to form his own organization, the name of which translates into English as "Those Who Sign with Their Blood." The departure came amid accusations he had been disobedient, used funds improperly, failed to attend meetings and did not answer phone calls from al Qaeda leadership, according to a report by the Associated Press.

"Why do the successive emirs of the region only have difficulties with you?," asks AQIM's council of religious leaders in a letter to Belmokhtar obtained by the AP, in which they refer to him by his nom de guerre "Abu Khaled.""Or are all of them wrong and brother Khaled is right?"

Belmokhtar's new organization was responsible for one of the most audacious terrorist acts in North Africa in recent years, when in January 2013 it captured a natural gas plant in Algeria. After the capture of some 800 hostages, a siege unfolded over two days, but by the time Algerian Special Forces ended the crisis, at least 35 foreign workers and one Algerian security guard were dead. Belmokhtar went on to lead an alliance of al Qaeda-linked Islamist militants calling itself al Murabitoun, which carried out attacks in Mali.

He has been reported dead several times before but always reappeared, earning "a reputation as one of the most elusive jihadi leaders in the region," reported the Guardian. In 2013, Chad's President Idriss Deby claimed Belmokhtar had blown himself up" in "despair" over the loss of a comrade. "We have proof of his death," he told French media, but said unfortunately "we couldn't film it."

Libyan authorities though, believe he has finally been killed. The country's internationally-recognized government claimed Belmokhtar was killed in a statement on Facebook on Sunday night. "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," it said.

U.S. officials said they were still assessing the results of the Saturday strike, but Pentagon spokesman Colonel Steve Warren said the military believed the strike was successful and hit the target. Neither U.S. officials nor the Libyan government provided proof of Belmokhtar's death, which likely requires a DNA test or an announcement by Belmokhtar's group that he was killed.

"I can confirm that the target of last night's counterterrorism strike in Libya was Mokhtar Belmokhtar," Warren said Sunday. "Belmokhtar has a long history of leading terrorist activities as a member of (al-Qaida in the Islamic Maghreb), is the operational leader of the al-Qaida-associated al-Murabitun organization in northwest Africa and maintains his personal allegiance to al-Qaida."

But an Islamist who spoke on condition of anonymity for fear of reprisals, told AP early Monday that Belmokhtar wasn't at the site of the U.S. airstrike. He said the strike killed four Ansar Shariah members in Ajdabiya, some 530 miles east of the Libyan capital, Tripoli.

American officials have linked Ansar Shariah to the September 11, 2012, attack on the U.S. Consulate in Benghazi.

The charges filed against Belmokhtar by federal law enforcement officials in Manhattan included conspiring to support al Qaeda and use of a weapon of mass destruction. Additional charges of conspiring to take hostages and discharging a firearm in furtherance of a crime of violence carry the death penalty.

If his death can be confirmed, he will be the latest veteran of the al Qaeda movement to be killed as the organization continues to struggle to remain the preeminent force for militant Islamism in the wake of Islamic State's ascendancy.

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