The United States denounced a suicide attack Monday that killed a Yemeni general who had led a major offensive against Al-Qaeda militants in the country's south.

General Salem Ali Qoton was killed when a suicide bomber threw himself on the officer's vehicle as he blew himself up, officials in Yemen said.

"The United States condemns in the strongest terms today's terrorist attack against Major General Salem Ali Qoton, southern regional commander of the Yemeni central security forces," said State Department spokeswoman Victoria Nuland, calling it a "cowardly attack."

"Major General Ali Qoton was leading the fight against Al-Qaeda in the Arabian Peninsula (AQAP) in southern Yemen and had recently achieved some very important successes in pushing AQAP out of several Yemeni cities," she told reporters.

A medic related to Qoton said the attacker brazenly shook hands with the general before blowing him up.

Yemeni President Abdrabuh Mansur Hadi blamed Al-Qaeda for the assault and vowed to "cleanse the country from the evil of terrorists," the official Saba news agency reported.

The attack on the army commander came as Al-Qaeda fled its last bastion in Yemen's restive southern and eastern provinces in the face of the military's month-long offensive designed to decimate the extremist network.

"The United States will continue to support President Hadi, and those who carry on the efforts of Major General Ali Qoton, as they work to realize a brighter, more prosperous future for the Yemeni people," she said.

The United States has sent military advisers to help Yemen in its fight against Al-Qaeda and officially confirmed last week taking lethal action against the group's members in Yemen and Somalia.

The targeting of Al-Qaeda militants in Yemen by armed US drones is an open secret, privately acknowledged by US officials.