Yemenis in the central city of Taiz and the capital Sanaa held the largest protests yet against a takeover by a Shi'ite Muslim militia group on Wednesday after the United States, Britain and France shut their embassies in Yemen over security fears.
Armed Houthi rebels seized more than 20 U.S. vehicles after the ambassador and diplomats left from the airport on Wednesday, local staff told Reuters. Embassy workers had already destroyed weapons, computers and documents, they added.
The Iranian-backed Houthi movement has called its seizure of power in Yemen a revolution and says it wants to rid the country of corruption and economic peril.
Yemen, which borders oil giant Saudi Arabia, had long been at the forefront of the U.S.-led war against al-Qaida, but the long-standing alliance between Washington and Sanaa appears to have ended for now.
The United States stopped work at its embassy Tuesday and withdrew its diplomatic staff. France and Britain followed suit on Wednesday.
Employees of the German embassy said its mission was also getting rid of sensitive documents and would soon close.
The Houthis, who overran Sanaa in September and formally took power last week, are stridently anti-American, and chant "death to America" at rallies.
Their leader Abdel Malik al-Houthi has also blasted what he calls Western meddling in Yemen.
"Recent unilateral actions disrupted the political transition process in Yemen, creating the risk that renewed violence would threaten Yemenis and the diplomatic community in Sanaa," U.S. State Department spokesperson Jen Psaki said.
But Houthi struck a conciliatory tone in a televised speech on Tuesday.
"It is in the interest of every power, domestic and foreign, to stabilize this country," he said.
But Houthi forces advanced far into the south on Tuesday night, according to local officials, continuing with their of expansion of recent months which has angered many and is raising fears of an all-out civil war.
Leaders and Sunni tribesmen in the southern and eastern regions, which the group has yet to seize, are arming themselves against their push and are in some cases making common cause with Yemeni al-Qaida militants.
Al-Qaida in the Arabian Peninsula (AQAP), one of the global militant group's most powerful arms, has repeatedly bombed and attacked Houthi targets along with the tribesmen.
Other tribes from Yemen's formerly independent South, which has clamored for secession for almost a decade, vowed on Wednesday to repel any Houthi attack.
The Houthi forces are bolstered by army units widely believed to maintain loyalty to ex-president Ali Abdullah Saleh.
Saleh and his former ruling party have denied an attempt to settle old scores and reassert its control over the country through the Houthis.
Houthi fighters, bedecked in tribal robes and automatic rifles, were out in force manning checkpoints and guarding government buildings they control in the capital.
Gunmen shot in the air and thrust daggers at hundreds of protesters opposing their rule.
In Taiz, which the Houthis do not control, huge crowds of tens of thousands carried banners and chanted slogans against the group.
Opponents of the Houthi group, including Yemen's rich Sunni Gulf Arab neighbours, have decried the takeover as a coup.
Those countries, along with Washington and the United Nations, helped craft a delicate plan that eased the veteran autocrat Saleh from power after Arab Spring prostests in 2011.
But the tenure of Saleh's successor, Abd-Rabbu Mansour Hadi, was defined by gridlock among Yemen's array of feuding parties. Hadi finally resigned last month along with his whole government after Houthi gunmen attacked his home.