Said al-Shihri, seen in this 2009 file photo when he was a prisoner at the U.S. prison in Guantanamo Bay, Cuba, was killed in Yemen, U.S. officials have confirmed. REUTERS/Handout

The No. 2 al-Qaeda leader in Yemen has been killed, dealing a major blow to the terror group, senior U.S. officials confirmed Monday.

The officials said Saeed al-Shihri was killed, but could not confirm any American involvement in the airstrike Monday that Yemeni leaders say killed the terrorist and five others.

The missile that killed al-Shihri, a Saudi national, was believed to have been fired by a U.S.-operated, unmanned drone aircraft, Yemeni officials said. The U.S. doesn't usually comment on such attacks although it has used drones in the past to go after al-Qaeda members in Yemen.

Two American officials spoke on condition of anonymity because they were not authorized to release the information to the news media.