UN Secretary General Ban Ki-moon has warned that Yemen is falling apart and called for action to avert chaos, as al-Qaeda fighters overran an army camp and seized heavy weaponry.
The UN chief was reporting to the 15-member Security Council after talks with Gulf officials that he said concentrated on "preventing civil war in Yemen".
"Let me be clear: Yemen is collapsing before our eyes. We cannot stand by and watch," Ban told the council.
Long on the front line of the war against Al-Qaeda, Yemen has descended into chaos since Shi'ite militiamen, known as Huthis, seized Sanaa in September and ousted the government last week.
The United States, Britain and France have rushed to close their embassies over security fears, with US staff destroying top-secret documents and sensitive equipment before pulling out on Wednesday.
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The Netherlands followed suit on Thursday, closing its Sanaa mission temporarily due to security concerns, the government said.
The Huthis said Western powers had no reason to shut their embassies.
Hussein al-Ezzi, described as the militia's foreign relations chief, said the closures were designed to "pressure" the Yemeni people.
"The decisions of some Western countries to close their embassies in Sanaa are absolutely unjustified," he was quoted as saying by the official Saba news agency, now under militia control.
UN special envoy for Yemen, Jamal Benomar, told the Security Council via video link from Sanaa that the country was "at a crossroad".
"Either the country will descend into civil war and disintegration, or the country will find a way to put the transition back on track," said Benomar, who has been leading efforts to broker a deal between Yemen's rival factions.
The Security Council last week threatened to "take further steps" if negotiations to end the crisis failed, in a veiled reference to possible sanctions.
The Huthis have been tightening their grip on Sanaa and expanding their control of territory to the south.
Last week, they dissolved parliament and declared a "presidential council" after Western-backed leader Abedrabbo Mansour Hadi resigned over what he said was an ungovernable situation.
Ban at the weekend called for Hadi to be fully restored as president, following talks with King Salman in Saudi Arabia, which has described the Huthi power grab as a coup.
Yemen has been a key ally in the fight against Al-Qaeda, allowing Washington to carry out a longstanding drone war on its territory.
But while Marines at the embassy departed, officials stressed there were still US special forces on the ground to carry on the fight.
On Thursday, seven people died in clashes as Al-Qaeda fighters seized the camp of the 19th Infantry Brigade in Baihan, in southern Shabwa province, and captured a large quantity of armour and heavy weaponry.
They took "30 tanks, 90 military vehicles, 25 armoured vehicles and 28 artillery pieces," a military official told AFP.
Al-Qaeda in the Arabian Peninsula (AQAP), considered by Washington as the jihadist network's most dangerous branch, confirmed it had seized the camp, accusing troops there of links with the Huthis.
