The United States has evacuated its remaining military personnel from Yemen because of the deteriorating security situation, US officials have confirmed.
On Saturday, Yemeni officials said about 100 US troops were leaving an air base near a southern city that was stormed by al-Qaeda fighters on Friday.
There has been mounting violence by rival armed groups in Yemen, including Houthi rebels, al-Qaeda and IS.
The UN Security Council is holding an emergency meeting on Yemen on Sunday.
It was requested by Yemeni President Abdrabbuh Mansour Hadi, who fled to the southern port city of Aden after the capital was taken over by Houthis last month.
In a letter sent to the UN, President Hadi called for an "urgent intervention" to stop the aggression "that is aimed at undermining the legitimate authority", according to Reuters news agency.
'No military solution'
Late on Saturday, US state department spokesman Jeff Rathke said: "Due to the deteriorating security situation in Yemen, the US government has temporarily relocated its remaining personnel out of Yemen."
He said the US would continue to support Yemen's "political transition" and monitor terrorist threats emanating from the country. but he added: "There is no military solution to Yemen's current crisis."
The US withdrawal from the al-Anad air base comes after an offensive by al-Qaeda fighters on the nearby city of al-Houta.
The militants were later pushed out of the city by Yemen's armed forces, officials said.
The US military personnel at the base, including some special forces, had been training Yemeni fighters to support their fight against al-Qaeda.
The US closed its embassy in Sanaa in February after Houthi rebels took over the city.
On Friday, President Hadi demanded that the rebels withdraw from Sanaa in his first televised address since fleeing the city.
Soon after Mr Hadi spoke, the Houthis called for a general mobilisation of their forces against those loyal to the president.
Yemen is the base of al-Qaeda in the Arabian Peninsula (AQAP), a powerful offshoot of the jihadist group.
However, IS is also gaining ground after setting up a base there in November. The group claimed a suicide attack on two Houthi mosques on Friday in the capital, Sanaa.
Both al-Qaeda and IS are Sunni groups and consider the Shia Muslim Houthis to be heretics.