Yemeni President Abd-Rabbu Mansour Hadi accused the Iranian-allied Houthi militia on Saturday of staging a coup against him and appealed to the United Nations for "urgent intervention", even as the United States evacuated its remaining forces.

In a call to arms from the southern city of Aden, where he fled last month after escaping house arrest by the Houthis, Hadi called on them to pull their forces out of state ministries, return weapons seized from the army and quit the capital, Sanaa.

The UN Security Council was set to meet on Sunday to discuss Yemen after Hadi appealed to the 15-member body for assistance "in all available means to stop this aggression".

Yemen has been hurtling towards civil war since last year when the Houthis seized Sanaa and advanced into Sunni Muslim areas, leading to clashes with local tribes and energizing a southern separatist movement.

US officials said Washington had evacuated its remaining personnel from Yemen, including about 100 special operations forces, because of deteriorating security, marking a further setback in US efforts against a powerful local al Qaeda branch.

The last major US military contingent in Yemen had been stationed at the al-Annad air base in the south, according to national security sources.

State Department spokesman Jeff Rathke said all remaining US staff had been "temporarily relocated" but insisted that Washington would "continue to actively monitor terrorist threats emanating from Yemen and ... take action to disrupt continuing, imminent threats to the United States".

Washington for years has been waging a campaign of deadly drone strikes against al Qaeda operatives in Yemen. US officials say the unmanned aircraft fly out of a base in neighboring Saudi Arabia.

Only last September US President Barack Obama touted the partnership with Yemen as a model in counter-terrorism.

But the subsequent collapse of Hadi's government disrupted some US counterterrorism operations, and the closing of the US embassy in Sanaa last month took a further toll.

Despite that, Hadi sounded a defiant note from his base in the south on Saturday, threatening action against the Houthis' northern stronghold.

"We shall deliver the country to safety and raise Yemen's flag on Mount Marran in Saadeh instead of the Iranian flag," he said in a televised speech, his first since reaching Aden. Iran is an ally of the Houthis, who belong to a Shi'ite Muslim sect.

The Houthis, in a statement from their Supreme Revolutionary Committee, did not directly respond to the speech but called for a "general mobilization" of the armed forces against a "dirty war" they said was being waged by militias loyal to Hadi.