Editor's Note: An earlier version of this story incorrectly cited U.S. officials as saying the strike killed Mokhtar Belmokhtar.
The U.S. military launched an airstrike in Libya on Sunday targeting a senior al Qaeda militant leader purportedly behind the deadly attack on an Algerian gas plant that left 38 foreigners dead.
The Libyan government said in a statement that the airstrike killed Mokhtar Belmokhtar. However, U.S. officials said they could not immediately confirm the militant leader's death.
The Pentagon confirmed that Belmokhtar was "the target" of a counterterrorism strike in Libya but said it was too soon to determine whether the strike had been successful.
"We are continuing to assess the results of the operation and will provide more details as appropriate," Pentagon spokesman Col. Steven Warren said in a statement.
U.S. military officials told NBC News that F-15 airstrikes dropped 500-pound bombs on a building believed to be housing Belmokhtar southwest of Benghazi. Officials said they believe Belmokhtar was killed in the strike but have no formal confirmation.
The U.S. had offered $5 million for information leading to the capture of Belmokhtar, an Algerian national who long served as a leader of al Qaeda in the Islamic Maghreb (AQIM).
He announced a split from AQIM in late 2012 to lead al Murabitoun, though the Pentagon's Warren noted that Belmokhtar "maintains his personal allegiance to al Qaeda."
Al Murabitoun claimed responsibility for the January 2013 attack on the Amenas gas plant in Algeria, which killed 38 foreigners — including at least three Americans.