U.S. Air Force Secretary Deborah Lee James has confirmed weekend airstrikes targeting an extremist leader linked to al-Qaida, and says the results of the raid are still being studied.

U.S. officials say the attack probably killed Mokhtar Belmokhtar, charged with leading the attack on a gas plant in Algeria in 2013 that killed at least 35 hostages. An Islamist with ties to Libyan militants cast doubt on the claim.

James told reporters at the Paris Air Show on Monday that "the impact of the raid is still being assessed."

She added, "We watched, we waited ... and precision weapons were used."

Belmokhtar, who reportedly lost his eye in combat and fought in Afghanistan, battled Algeria's government since the 1990s and then joined al-Qaida before branching out with his own group.