During Yemen's 2011 uprising, al-Qaeda occupied large sections of the south before being driven out by the new government. Al-Qaeda has retaliated with assassinations and bombings at military compounds.
The official says the soldiers were killed Saturday when al-Qaeda fighters attacked a military checkpoint in Radda.
Another security official says Colonel Ahmed Abdel-Razaq, who was the intelligence chief in Mukalla, the capital of southern Hadramawt province, was killed Saturday by two gunmen on a motorcycle.
Both officials spoke on condition of anonymity because they were not authorized to speak to the media.