Militants stormed the Defense Ministry in the heart of Yemen’s capital Thursday, killing 52 people, including at least seven foreigners, in a suicide car bombing and assault by gunmen. The brazen, al-Qaida-style attack follows a rise in U.S. drone strikes in this key American ally in the Middle East.

The two-stage operation came as the defense minister was in Washington for talks. The U.S. military increased its regional alert status after the attack and is “fully prepared to support our Yemeni partners,” a senior U.S. defense official said.

At least 167 people were wounded, nine seriously, in the bombing and fierce firefight, which underscored the ability of insurgents to take advantage of Yemen’s instability and tenuous security — even at the headquarters of its military.

Among the dead at the Defense Ministry complex, which also houses a military hospital, were soldiers and civilians, including seven foreigners — two aid workers from Germany, two doctors from Vietnam, two nurses from the Philippines and a nurse from India, according to Yemen’s Supreme Security Commission, which issued the casualty figures. Among the Yemeni civilians killed were a doctor and a senior judge, it said.

There was no immediate claim of responsibility for the attack, the deadliest in Sanaa since May 2012. Such 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 most active in the world. In recent months, Washington has sharply escalated drone attacks against the militants in the impoverished nation. U.S. forces also have been training and arming Yemeni special forces, and exchanging intelligence with the central government.

The terrorist network gained a major foothold in the south, taking over several towns in 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.

Al-Qaida’s Yemen branch is linked to the foiled plot on Christmas 2009 in which a passenger on a Detroit-bound plane allegedly tried to detonate explosives in his underwear, as well as explosives-laden parcels intercepted on cargo flights a year later.

Defense Minister Mohammed Nasser Ahmed was in Washington for consultations with U.S. officials, part of a “strategic dialogue” to aid Yemen’s political transition and security cooperation.

Thursday’s attacks “will not deter the security forces, the armed forces and the honorable sons of the nation from carrying out their religious and patriotic duty in the face of terrorists wherever they may be,” the Supreme Security Commission said in a statement. The commission is led by President Abed Rabbo Mansour Hadi, who succeeded Saleh, and includes the country’s top military and intelligence officials.

The senior U.S. defense official said the U.S. military “has increased its regional alert status following the terrorist attack on the Yemeni Republic Ministry of Defense.”

“The United States military is fully prepared to support our Yemeni partners in the wake of this incident,” added the official, who was not authorized to speak publicly about the matter and requested anonymity.

The U.S. State Department condemned the attack.

“We stand with Yemen against this violence and remain firmly committed to supporting the Yemeni people,” said a statement from the State Department’s deputy spokeswoman, Marie Harf.