"We do not have clear information about exactly what happened, whether it is al-Qaeda or other armed groups. The government is facing [resistance] from a separatist movement in the south of Yemeni, so it it's not clear."
The attackers were armed with rocket-propelled grenades, assault rifles and grenades, one witness said.
Police are blaming al-Qaeda operatives in the region for the assault.
Hakim al-Masmari, editor-in-chief of the Yemen Post, told Al Jazeera: "Our sources confirm that the attack was from al-Qaeda ... I think al-Qaeda is trying to make a strong presence in the south to make the Yemeni government having the idea of a separation less practical."