Militants from al-Qaeda in the Arabian Peninsula (AQAP) have seized an airport in southern Yemen, officials say.
Troops guarding the site in the major port city of Mukalla, Hadramawt province, have fled, they said.
AQAP has exploited the chaos gripping the country, overrunning Mukalla earlier this month and freeing inmates from a prison.
A Saudi-led coalition has been bombing Shia Houthi rebels, who have been advancing across the country.
The Houthis swept into the capital Sanaa last September, eventually forcing President Abdrabbuh Mansour Hadi to flee abroad.
AQAP fighters have also reportedly took control of a sea port and an oil terminal in southern Yemen.
As the coalition strikes continue against the Houthis, Yemeni Vice-President Khaled Bahah said he did not want a Saudi-led ground offensive.
With the raids failing to stop the rebels, there has been speculation a ground campaign could be launched.
But Mr Bahah said: “We are still hoping that nothing will happen, and we are not expanding the war, but we are trying to stop the war.”
Earlier, it was announced the UN’s special envoy to Yemen, Jamal Benomar, has stepped down from his post.
The UN said it would name a successor “in due course” and “spare no efforts to relaunch the peace process”.
The Moroccan diplomat is believed to have come under pressure to resign from Saudi Arabia and other Gulf states after he failed to get the warring Yemeni factions to attend peace talks.
Houthis – The Zaidi Shia Muslim rebels from the north overran Sanaa last year and then expanded their control. They want to replace Mr Hadi, whose government they say is corrupt. The US alleges Iran is providing military assistance to the rebels.
Ali Abdullah Saleh – Military units loyal to the former president – forced to hand over power in 2011 after mass protests – are fighting alongside the Houthis.
Abdrabbuh Mansour Hadi – The president fled abroad in March as the rebels advanced on Aden, where he had taken refuge in February. Sunni Muslim tribesmen and Southern separatists have formed militia to fight the rebels.
Saudi-led coalition – A US-backed coalition of nine, mostly Sunni Arab states says it is seeking to “defend the legitimate government” of Mr Hadi.
Al-Qaeda in the Arabian Peninsula – AQAP opposes both the Houthis and President Hadi. A rival affiliate of Islamic State has also recently emerged.