Suspected al Qaeda-linked militants killed at least 14 Yemeni soldiers and security guards on Saturday in a car bomb and grenade attack on the intelligence service headquarters in the southern port city of Aden.
More bodies were believed to be buried under the rubble of the building, part of which was levelled in the assault, the defence ministry said.
At least seven people were wounded.
The United States has been pouring aid into Yemen to stem the threat of attacks from al Qaeda in the Arabian Peninsula and to try to prevent any spillover of violence into neighbouring Saudi Arabia, the world's top oil exporter.
