Hours later, the State Department announced the U.S. Embassy in Yemen was closing to the public “until further notice” over security concerns as street gunbattles and political turmoil continue to roil this impoverished Arab country.

The drone strike was also the first such U.S. action since Shiite rebels known as Houthis placed embattled President Abed Rabbo Mansour Hadi and his Cabinet under house arrest last week in an attempt to force them to make political concessions. After reaching a tentative deal with the Houthis, the president and his government resigned in an effort to thwart rebel attempts to force more compromises.

Yemeni tribal and security officials in the central province of Marib said a missile hit a vehicle carrying three men near the boundary with neighboring Shabwa province, an al-Qaida stronghold.

An al-Qaida member told The Associated Press that one of the three slain fighters was Saudi while the other two were Yemenis. He identified the Saudi man as Awaid al-Rashidi, who he said was in his 30s and had been imprisoned in Saudi Arabia for seven years, apparently over terrorism charges. The two Yemeni al-Qaida members killed in the strike were Abdel-Aziz al-Sanaani and Mohammed al-Jahmi from Marib’s tribe of Jahmi, the member said.

Both Yemeni officials and the al-Qaida member spoke on condition of anonymity because they were not authorized to speak to media.

The Houthis, who claim to only want an equal share of power, had seized the capital of Sanaa and its central province in September and at least eight other provinces, after descending from their northern stronghold.

Critics say the Shiite Houthi rebels want to retain Hadi as president in name only, while keeping an iron grip on power. They also accuse the Houthis of being a proxy of Iran, an allegation the rebels deny.

The prospect of a leaderless Yemen has raised concerns about Washington’s ability to continue targeting Al-Qaida in the Arabian Peninsula, as the Yemeni branch is known. The group claimed the recent attack on a French satirical weekly and has mounted several failed attacks on the U.S. homeland.

The Houthis are staunch opponents of al-Qaida but in their push into Sunni-dominated areas, they risk driving locals into the arms of al-Qaida insurgents and turning their power struggle into sectarian warfare. The Houthis are Zaydis, a Shiite minority that makes up about a third of Yemen’s population.

Monday’s strike came a day after President Barack Obama defended his counterterrorism strategy in Yemen, saying his approach “is not neat and it is not simple, but it is the best option we have.” He ruled out deploying U.S. forces there.

“The alternative would be massive U.S. deployments in perpetuity, which would create its own blowback and cause probably more problems than it would potentially solve,” Obama said during a joint media appearance with Indian Prime Minister Narendra Modi.

Obama said that while he was concerned about the fragility of Yemen’s central government, the country “has never been a perfect democracy or an island of stability.”

In September, as Houthis were on the march to take Sanaa, Obama cited Yemen as a terrorism success story as he outlined his strategy against the Islamic State in Iraq and Syria, which involves targeted U.S. strikes against militants with the cooperation of a friendly ground force. Obama called it an approach “that we have successfully pursued in Yemen and Somalia for years.”

Some U.S. lawmakers raised concerns about Obama’s broader anti-terror strategy. Republican Senator John McCain told CBS’ “Face the Nation” that more special operations forces may be need in countries battling extremists.

“We need more boots on the ground,” said McCain, who is also the chairman of the Senate Armed Services Committee. “I know that’s a tough thing to say, and a tough thing for Americans to swallow. But it doesn’t mean the 82nd Airborne. It means forward air controllers. It means special forces, it means intelligence, and it means other capabilities.”

Led by Osama bin Laden’s top aide Nasser al-Wahishi, al-Qaida has posed the greatest danger to Western interests, especially the United States. After several unsuccessful operations on U.S. soil, the group claimed responsibility for this month’s bloody rampage at the office of a French satirical newspaper that left 12 dead, to avenge cartoons depicting the Prophet Muhammad.

Last year, at least 23 U.S. drone strikes killed 138 al-Qaida militants as well as some civilians, according to the Long War Journal, which tracks militant groups. U.S. officials rarely comment on the covert drone program. However, the number of strikes is much smaller compared to 2012 when the U.S. carried out 41 airstrikes that killed some 190 militants in Yemen.

The airstrikes’ campaign has had its pitfalls, with dozens of civilians killed or badly wounded in the crossfire, feeding anti-American sentiment among large sectors of Yemenis and prompting disgruntled tribesmen to become easy recruits to al-Qaida.

In the Yemeni capital of Sanaa, the Houthis showed no tendency of de-escalating the political crisis, sending militiamen armed with knives and batons to attack and detain demonstrators who were protesting on Monday against their power grab.

The militiamen dispersed those who tried to converge on Sanaa’s Change Square— the epicenter of Yemen’s 2011 popular uprising that led to the ouster of Hadi’s predecessor, longtime autocrat Ali Abdullah Saleh. Saleh is believed to be a strong backer of Houthis.

A well-known activist, Adel Shamsan, said in an audio recording circulated by Yemeni activists on Twitter that the Houthis brought “thugs” who chased away the protesters, accusing them of being “American agents.”

Shamsan said he was briefly held by the militiamen before escaping.