Armed rebels in Yemen’s capital of Sanaa seized U.S. embassy vehicles Wednesday after diplomats fled the country over growing unrest.

Pentagon spokesman Col. Steve Warren confirmed that the vehicles were taken by Houthi rebels after embassy personnel and U.S. Marines guarding the embassy evacuated.

Warren said the Marines turned over their small arms to government officials before boarding a commercial flight from Sanaa.  

Marines “destroyed the larger weapons” before leaving Yemen Tuesday, Warren said. 

Members of the embassy staff told Reuters that more than 20 vehicles were taken by the rebels after the Americans left Sanaa’s airport.

Late Tuesday, the State Department announced that the U.S. Embassy in Yemen had been closed and evacuated after much of the country was taken over by Shiite rebels last month.

Hours later, Britain and France followed suit and ordered their citizens to leave Yemen as soon as possible.

The U.S. embassy had already been operating with severely reduced staff for several weeks. State Department spokesman Jen Psaki said remaining diplomatic personnel had been relocated "due to the ongoing political instability and the uncertain security situation."

Yemen has been in crisis for months, with Houthi rebels besieging the capital and then taking control and forcing the resignation of the U.S. and Saudi-backed president and his government.

"The security situation in Yemen has continued to deteriorate over recent days," U.K. Minister for the Middle East Tobias Ellwood said in a statement. "Regrettably we now judge that our embassy staff and premises are at increased risk." Ellwood also urged all British citizens still in Yemen to "leave immediately."

In a statement on its website, the French Embassy said it would close as of Friday.

The embassy closures were announced as Houthi rebels, armed with Kalashnikov assault rifles and dressed in police uniforms and civilian clothes, patrolled the main boulevards of the capital, Sanaa, some in pickup trucks mounted with anti-aircraft guns.

Scattered protests could be seen in the city, with demonstrators denouncing the Houthis for taking power and dissolving parliament. Shops closed early and helicopters also hovered overhead.

Houthis attacked one demonstration, stabbing and beating protesters trying to reach the local United Nations office, witnesses said. The rebels detained a number of people as well, they said.

Earlier Tuesday, U.S. officials told the Associated Press that the embassy closure would not affect ongoing operations against the terror group Al Qaeda in the Arabian Peninsula (AQAP).

"The United States remains firmly committed to supporting all Yemenis who continue to work toward a peaceful, prosperous and unified Yemen," Psaki said. "We will explore options for a return to Sanaa when the situation on the ground improves."

A group of Islamist fighters in Yemen renounced their loyalty to Al Qaeda's leader and pledged allegiance to ISIS, Reuters reported Wednesday, citing a Twitter message retrieved by U.S.-based monitoring group SITE.

"We announce breaking the pledge of allegiance to the sheikh, the holy warrior and scholar Sheikh Ayman al-Zawahiri ... We pledge to the caliph of the believers Ibrahim bin Awad al-Baghdadi to listen and obey," they reportedly said.

The State Department issued a travel warning advising U.S. citizens to defer travel to Yemen and urging U.S. citizens currently living in Yemen to depart.

Two U.S. officials said Marines providing the security at the embassy will also likely leave, but American forces conducting counterterrorism missions against Al Qaeda's Yemen affiliate in other parts of the country would not be affected. The U.S. officials spoke on condition of anonymity because they were not authorized to discuss the closure publicly on the record.

Although operations against AQAP will continue, the closure of the embassy will be seen as a blow to the Obama administration, which had held up its partnership with ousted Yemeni President Abed Rabbo Mansour Hadi's government as a model for his strategy in combatting terrorism, particularly in unstable countries.

"Yemen has never been a perfect democracy or an island of stability," President Barack Obama said late last month as conditions in the capital of Sanaa became worse. "What I've said is, is that our efforts to go after terrorist networks inside of Yemen without an occupying U.S. army, but rather by partnering and intelligence-sharing with that local government, is the approach that we're going to need to take."

The embassy closure will also complicate the CIA's operations in Yemen, U.S. intelligence officials acknowledge. Although CIA officers could continue to work out of U.S. military installations, many intelligence operations are run from embassies, and the CIA lost visibility on Syria when that embassy was evacuated in 2012. The CIA's main role in Yemen is to gather intelligence about members of Al Qaeda in the Arabian Peninsula and occasionally kill them with drone strikes. Both the CIA and the military's Joint Special Operations Command run separate drone killing programs in Yemen, though the CIA has conducted the majority of the strikes, U.S. officials have said.

There were 23 U.S. drone strikes reported in Yemen last year, 26 in 2013 and 41 in 2012, according to Long War Journal, a website that tracks them through media reports.

The Houthis last week dissolved parliament and formally took over after months of clashes. They then placed President Hadi and his Cabinet ministers under house arrest. Hadi and the ministers later resigned in protest.

Earlier Tuesday, Yemeni military officials said the Houthis, aided by troops loyal to Hadi's predecessor, former President Ali Abdullah Saleh, took full control of the key central province of Bayda province.

The U.S. Embassy in Yemen is the third in an Arab country that has closed since the turmoil of the Arab spring began in December 2010. The other two were embassies in Damascus, Syria and Tripoli, Libya. The embassy in Damascus was closed in Feb 2012 and the embassy in Tripoli was closed in July 2014.

The embassy in Yemen was operating with only a small portion of its usual diplomatic staff and had closed to the public for all but emergency services in January. It had been operating with reduced manpower since September 2014, when the State Department ordered all non-essential personnel to leave the country.

In May 2014, the embassy in Sanaa was closed for several weeks due to heightened security threats.

The Associated Press contributed to this report.