BENGHAZI, Libya — The U.S military says it launched weekend airstrikes targeting and likely killing an al-Qaida-linked militant leader in eastern 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 Mokhtar Belmokhtar, instead killing four members of a Libyan extremist group the U.S. has linked to the Sept. 11, 2012, attack on the U.S. Consulate in Benghazi that killed Ambassador Chris Stevens and three other Americans.

U.S. officials said they are still assessing the results of the Saturday strike, but Pentagon spokesman Col. Steve Warren said the military believes 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.”

A U.S. official said two F-15 fighter jets launched multiple 500-pound bombs in the attack. The official was not authorized to discuss the details of the attack publicly so spoke on condition of anonymity. Authorities say no U.S. personnel were on the ground for the assault.