The official said dozens of militants stormed the headquarters of the Yemeni army's Second Division in the city of al-Mukalla and had captured some military personnel. At least six people were wounded.

"They caused confusion because soldiers at the base thought they were being attacked by members of the Central Security apparatus," the official said.

He said special forces personnel had been flown from Sanaa to Mukalla ahead of an expected operation to retake the base.

A resident said he heard several explosions and that the army had cordoned off the area leading to the military base. He said the army had asked residents of more than 50 houses in the vicinity of the base to evacuate their homes.

Yemen is battling one of the most active branches of al Qaeda, known as al Qaeda in the Arabian Peninsula (AQAP).

On September 20, suspected al Qaeda militants killed dozens of Yemeni soldiers and policemen in attacks in the south, which officials described as the deadliest for more than a year.

Dozens of Yemeni security and military officers have been killed in the past two years, many by bombs planted in their cars or drive-by shootings, often blamed on AQAP or affiliated groups.

Intelligence pointing to an impending attack by AQAP prompted the United States and other Western countries to close many of their embassies temporarily in the Middle East, Africa and Asia last month.

The militants took advantage of political chaos in Yemen during the Arab Spring in 2011 to seize control of some towns and surrounding areas in the south of the country.

They were beaten back by Yemeni forces and scattered into small groups spread across the country's rugged, remote southern terrain.

NJF/NJF