SANAA, Yemen -- Officials say the death toll from a suicide bombing at a military parade rehearsal in the capital Sanaa has risen to 38 troops.
The military officials say the Monday's bombing near Sanaa's presidential palace is one of the deadliest attacks in the city in months.
They said the attacker was a soldier taking part in the drill, lining up with fellow troops at a main square in the capital.
The officials spoke on condition of anonymity because they were not authorized to speak to the media.
The bomber detonated his explosives minutes before the arrival of the defense minister and the chief of staff, who were expected to greet the troops, the officials said. The drill was a rehearsal for a parade for the celebration of Yemen's National Day on Tuesday.
The attack left a scene of carnage, with scores of bleeding soldiers lying on the ground as ambulances rushed to the scene.
Meanwhile, Yemeni security officials said three U.S. Coast Guard trainers came under attack on Sunday by militants belonging to an al-Qaida front group in the Red Sea port city of Hodeida.
The three Americans were traveling in a car near their hotel when the militants pulled up in another vehicle and sprayed them with machine-gun fire. One was injured, the officials said Monday, speaking on condition of anonymity because they were not authorized to speak to the media.
In Sanaa, no one immediately claimed responsibility for Monday's suicide bombing, but the soldiers targeted were mostly troops from Yemen's Central Security, a paramilitary force commanded by Yahya Saleh, a nephew of ousted president, Ali Abdullah Saleh.
Saleh stepped down in February as part of a U.S.-backed power-transfer deal brokered by Gulf Arab countries. It gave Saleh immunity from prosecution in return for relinquishing his power.
Since then, the new president, Abed Rabbo Mansour Hadi, has pledged to restructure the army and purge it from Saleh's family members and loyalists suspected of hindering reforms.
Hadi has also vowed to step up the fight against al-Qaida, which expanded its foothold after exploiting the political and security turmoil in the wake of the uprising against Saleh.
Since the revolt erupted, inspired by other Arab Spring uprisings, al-Qaida militants overran large swaths of territory and several towns and cities in the south, pushing out government forces and establishing their own rule.
In recent weeks, the army has launched a concerted effort to uproot the militants from their strongholds -- and is closely coordinating with a small contingent of U.S. troops who are helping guide the operations from inside Yemen.