ADEN, Yemen (AP) -- A suicide car bomber struck Yemen's Defense Ministry Thursday, killing 18 soldiers and paving the way for a carload of gunmen wearing army uniforms to storm the heavily guarded compound in the capital of Sanaa, military and hospital officials said.
The brazen morning attack underlined the ability of insurgents to strike at the heart of the government as they exploit the instability that has plagued the U.S.-allied country for more than two years. Yemen's Defense Minister Mohammed Nasser Ahmed was in Washington on Thursday for talks with U.S. officials.
Nobody immediately claimed responsibility for the attack, but suicide bombings and complex attacks are the hallmarks of al-Qaida.
The U.S. considers Yemen's al-Qaida branch, known as al-Qaida in the Arabian Peninsula, to be the world's most active and has in recent months sharply escalated drone attack targeting the militants. American forces also have been training and arming Yemeni special forces, and exchanging intelligence with the central government.
The terror network gained a major foothold in the south, taking over several towns amid the chaos that followed the 2011 uprising that ousted longtime President Ali Abdullah Saleh. The drone strikes and a series of U.S.-backed military offensives helped uproot several key militant strongholds, but al-Qaida continues to fight back.
The military officials said the attack may have been timed to target a planned meeting of top commanders but missed because the meeting had been delayed until later in the morning.
They also said that two army vehicles went missing from the complex last month, but they did not know whether those were used in Thursday's attack.
The Defense Ministry got a tip last week that a major attack was imminent in the capital, prompting authorities to reinforce army and security forces normally deployed in Sanaa, the officials said.
Thursday's blast badly damaged a military hospital inside the complex, wounding two Germans who were part of a visiting medical team. It also blew out windows and the doors of nearby homes and offices, as well as destroying an armored vehicle and reducing three cars outside to charred hulks.
Military helicopters hovered over the aftermath as soldiers and ambulances arrived and gunfire echoed in the streets.
Hospital and military officials gave the death toll and said at least 40 people, most soldiers, also were wounded.
The Defense Ministry said "most" of the gunmen - who were armed with assault rifles and grenades - also were killed but did not give a number or more details.
President Abed Rabbo Mansour Hadi, who succeeded Saleh, later met with military commanders inside the devastated complex. He also ordered an investigation into the incident, military officials said.
Al-Qaida militants are concentered in the southern and eastern parts of Yemen, but they occasionally strike in the capital.
Yemen is strategically located at the southwest corner of the Arabian Peninsula, bordering Oman and Saudi Arabia, two of Washington's closest Arab allies. Yemen has a shoreline on the Red Sea and the Arabian Sea close to the vital shipping lines carrying oil from the energy-rich Gulf region to the West.