U.S. fighter jets have patrolled Yemen's northern border with Saudi Arabia as Yemeni forces hunt for Al Qaeda operatives, a security official said Saturday.

The official, speaking on condition of anonymity, said U.S. jets were patrolling the border provinces of Marib and Jawf, strongholds of Muslim militants where the Al Qaeda terror group is believed to be active.

The official said operations were designed to "tighten the grip on Al Qaeda suspects who are believed to be relocating in these tribal strongholds in the wake of the latest U.S. attack."

Tribal leaders in the region said Americans have also been seen on the ground aiding Yemenis special forces troops.

U.S. officials at the Pentagon and National Security Council did not immediately return phone calls seeking comment.

Earlier this month, a Hellfire missile from a CIA unmanned Predator drone killed six men, including Al Qaeda's alleged top operative in Yemen.

The missile strike also killed Kamal Derwish, the alleged leader of a terrorist cell based in Buffalo, N.Y. with links to Al Qaeda.

An Interior Ministry official, also speaking on condition of anonymity, told The Associated Press the other four men in the vehicle were members of the outlawed Adan-Abyan Islamic Army, a radical group of men who fought in Afghanistan in the 1980s.

The group was blamed for the 1998 kidnapping and killing of four Western tourists and a series of bombings in 2001 targeting a church, the Aden offices of the official news agency, and other sites.

On Friday, tribesmen and officials reported that military patrols had been stopping passenger vehicles for identity checks and that new checkpoints had been established in Marib and Jawf.

One tribal leader said that Americans had been seen working along with Yemeni government special forces, especially in Marib province.

Yemeni government officials refused to confirm the reports on the record. However, another Interior Ministry official, speaking on condition of anonymity, said the military operations were part of new security arrangements, which the government approved at a Cabinet meeting Tuesday.