Security officials said the base in Yemen’s Hadramawt province is supposed to be protected by several check points leading to its main gate, but that no security was posted outside the military compound when the attack took place.
The military sent in reinforcements and troops are now surrounding the compound, the officials said.
The attack underscores Al-Qaeda’s ability to exploit security lapses in Yemen, despite a dramatic rise in the number of US drone strikes on militants there—including in Hadramawt—since President Barack Obama took office.
This month the group launched an assault that killed 38 soldiers in a nearby province. Washington says the local Yemeni branch is one of the world’s most dangerous offshoots of the Al-Qaeda network.
In the Monday attack, authorities believe at least 15 militants stormed into the base, east of the city of Mukalla, in stolen military vehicles. They threw explosives at the main gate and gunned down security guards before overtaking the facility after a brief firefight inside, officials said.
Officials have not released a death toll.
A colonel who works at the base but who was not there when it came under attack says he received phone calls from comrades inside who alerted him to the attack.
The officials and colonel spoke on condition of anonymity because they were not authorized to speak to the media.
For a time, Al-Qaeda in the Arabian Peninsula, as the group is known in Yemen, was perhaps the most powerful offshoot in the region. In 2011, during political turmoil in Yemen, Al-Qaeda fighters temporarily seized control of a string of cities and towns in the south, where they remain active.