At least 14 soldiers and security guards were killed in Yemen and seven others wounded in a grenade attack on the headquarters of the intelligence service in the port city of Aden on Saturday.
More bodies were believed to be buried under the rubble of the building.
Al Qaeda is suspected. The building was attacked from two sides, with rocket-propelled grenades and automatic weapons used.
There has been a series of suicide bombings at military and security targets in Yemen since June.
In May, more than 90 people died in a suicide bomb attack at a military parade rehearsal in the capital, Sanaa.