The US is withdrawing its troops from al-Anad air base in Yemen because of increasing insecurity there, Yemeni sources say.
About 100 troops, including Special Forces commandos, are leaving the base near the southern city of al-Houta, the officials said.
Al-Houta was stormed by al-Qaeda fighters on March 20, although they were later driven out by the Yemeni army.
The US military has not confirmed the evacuation.
It comes a day after suicide bombers killed at least 137 people in the capital Sanaa. Militants allied to Islamic State (ISIS) said they carried out the attack.
There are mounting tensions between various powerful, armed elements in Yemen, including Houthi rebels, al-Qaeda and ISIS.
US troops at al-Anad air base have been training Yemeni fighters to launch attacks against al-Qaeda operatives.
On March 20, al-Qaeda fighters took control of al-Houta, near to the airbase. But the militants were later driven back by the army.
The US closed its embassy in Sanaa in February after Houthi rebel forces took over the city.
Yemen is the base of al-Qaeda in the Arabian Peninsula (AQAP), a powerful offshoot of the jihadist militant group.
ISIS is also gaining ground in Yemen, after setting up a base in the country in November.
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Former Yemeni President Abd Rabbuh Mansur Hadi has fled the capital, Sanaa, weeks after he was put under house arrest by Houthi rebels who forced him to resign.
Abd Rabbuh Mansur Hadi is thought to have reached the main southern city of Aden.
It comes a day after rival parties agreed on the formation of a transitional council to govern the country.
Yemen has been in crisis since the takeover by the Houthis, a Shia group.
UN mediator Jamal Benomar announced the preliminary accord between feuding factions on Thursday and hailed it as “an important step”.
Abd,Rabbuh Mansur Hadi’s supporters in Aden have so far refused to recognize what they denounce as a political coup.
Last week, the governors of the provinces of Aden, Lahij and Mahra demanded the reinstatement of Abd Rabbuh Mansur Hadi and reaffirmed their support for Yemen becoming a federation of six regions.
Houthi rebels seized the capital Sanaa in September, before capturing the presidential palace and placing Abd Rabbuh Mansur Hadi under house arrest. He then quit his presidential post, saying he could not continue under such pressure.
The Houthis dissolved parliament and installed a five-member “presidential council” on February 6.
This sparked security concerns that saw several Arab and Western states close their embassies and remove diplomats.
Since overrunning Sanaa, the Houthis have expanded their control to coastal areas and regions south of the capital.
Their takeover was denounced as a coup by rival political factions and prompted mass protests, mainly from the country’s Sunni majority.
The Houthis have also faced fierce resistance from Sunni tribes and al-Qaeda militants.