Government forces have been battling fighters loyal to the local branch of al Qaeda for more than a year, but not made lasting headway.

The United States has carried out dozens of drone strikes against militants in Yemen, including the radical American-born cleric Anwar al-Awlaki, who was killed in September.

U.S. officials said last month they had foiled a plot to bring down a U.S.-bound aircraft with a device that originated in Yemen.

The plot was brought to authorities' attention by a mole who infiltrated al Qaeda, a source in the region told CNN.

The mole works for Saudi intelligence, which has cooperated with the CIA for years, the source said.

Information from the mole also led to a drone strike this month that killed Fahd al Quso, 37, whom the U.S. considered a senior operative of al Qaeda in the Arabian Peninsula.