Yemen violence rages: Blast follows U.S. shooting (CBS/AP) SANAA, Yemen - A suicide bomber killed at least 60 Yemeni soldiers at a military parade rehearsal in the capital Sanaa on Monday in one of the deadliest attacks in the city in months, officials said. The bombing comes a day after militants opened fire on three U.S. Coast Guard trainers, injuring one, in the Red Sea port city of Hodeida. The suicide attack left a scene of carnage, with scores of bleeding soldiers lying on the ground as ambulances rushed to the scene. Several severed heads were on the pavement amid large pools of blood with scattered body parts and bits of human flesh around. "This is a real massacre," said Ahmed Sobhi, one of the soldiers who witnessed the explosion. There are piles of torn body parts, limbs, and heads. This is unbelievable. Military officials said the suicide bomber was a soldier taking part in the drill, lining up with fellow troops at a main square in the capital, not far from the presidential palace. 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. Meanwhile, Yemeni security officials said attackers who fired on the U.S. military personnel belong to an al Qaeda front group. 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 Qaeda, 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 Qaeda 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.