The United States said it had evacuated all its staff from Yemen, whose embattled president has appealed for "urgent intervention" by the UN Security Council as attacks by Iran-backed rebels bring his country nearer to civil war.
"Due to the deteriorating security situation in Yemen, the US government has temporarily relocated its remaining personnel out of Yemen," State Department spokesman Jeff Rathke said in a statement.
The evacuation comes after several suicide bombings claimed by the Islamic State group killed 142 people in Sanaa on Friday, with the jihadists seeking to exploit the chaos gripping the country.
The impoverished nation is torn between a north controlled by Iran-backed Shiite Huthi rebels and a south dominated by allies of President Abedrabbo Mansour Hadi, who fled house arrest in Sanaa to Aden in February.
The Huthi militia and its allies on Sunday seized the airport in the battleground central town of Taez from forces loyal to Hadi, security sources said.
Taez is strategically located on the road between Sanaa, which the Huthis overran in September, and the southern city of Aden, to which Hadi fled last month after escaping house arrest in the capital.
The UN Security Council is to hold an emergency meeting Sunday following Hadi's appeal.
In his letter to the Council, Hadi denounced "the criminal acts of the Huthi militias and their allies," saying they "not only threaten peace in Yemen but the regional and international peace and security."
"I urge for your urgent intervention in all available means to stop this aggression that is aimed at undermining the legitimate authority, the fragmentation of Yemen and its peace and stability," Hadi wrote.
Yemen has been torn by unrest since ex-strongman Ali Abdullah Saleh stepped down in early 2012 after a year-long popular uprising against him, with powerful armed groups sidelining the government since.
The country is now on the brink of civil war, with a deepening political impasse and an increasingly explicit territorial division along sectarian lines, with rising violence between the Huthi and Sunni tribes and Al-Qaeda.
- 'Two sides of same coin' -
Washington late Friday pulled out troops from the Al-Anad airbase in southern Yemen amid fighting involving Al-Qaeda militants nearby which left at least 29 dead.
The US would "continue to actively monitor terrorist threats emanating from Yemen and have capabilities postured in the area to address them," Rathke said.
Yemen has acknowledged that US personnel gathering intelligence for drone strikes on Al-Qaeda are deployed at Al-Anad.
Hadi pledged Saturday to fight Iranian influence in his country, accusing the Huthis of importing Tehran's ideology.
The Huthis, who seized Sanaa in September, vowed to take further "revolutionary steps" following Friday's blasts.
Signup to our newsletter and follow us on Facebook and Twitter!
In his first televised speech since he fled to Aden from house arrest in Sanaa, Hadi said he would ensure that "the Yemeni republic flag will fly on the Marran mountain in (the Huthi militia's northern stronghold) Saada, instead of the Iranian flag".
"The Iranian Twelver (Shiism) pattern that has been agreed upon between the Huthis and those who support them will not be accepted by Yemenis, whether Zaidi (Shiites) or Shafite (Sunnis)," he said.
The Huthis belong to the Zaidi offshoot of Shiite Islam. They are believed to have converted to Twelver Shiism, which is followed by Iran, but insist that Tehran does not meddle in Yemeni affairs.
In a letter to relatives of the mosque bombings victims, Hadi condemned the attacks as "terrorist, criminal and cowardly".
"Such heinous attacks could only be done by the enemies of life," who want to drag Yemen into "chaos, violence and internal fighting", he said.
"Shiite extremism, represented by the armed Huthi militia, and Sunni extremism, represented by Al-Qaeda, are two sides of the same coin, who do not wish good and stability for Yemen and its people."
Hadi has declared Aden the country's temporary capital.
Friday's bombings came a day after clashes in the southern city between Hadi loyalists and forces allied with the Huthis.
- 'Tip of the iceberg' -
Since taking Sanaa the Huthis have tightened their grip on government institutions, aided by loyalists of former president Saleh.
But in their push to widen their control to the south, they have faced fierce resistance from Sunni tribes allied with Al-Qaeda.
Al-Qaeda distanced itself from Friday's bombings, insisting it does not target mosques.
In an online statement claiming responsibility, the Sanaa branch of IS said the attacks were "just the tip of the iceberg".
Iran "strongly condemned" the bombings.
Mohammed Abdulsalam, spokesman for the Huthis' Ansarullah party, called the attacks part of a "clear war against the Yemeni people and its popular revolution" -- a reference to Sanaa's takeover.
"It is now imperative that we complete the revolutionary steps to protect the people and their revolution," he said in a statement.
The threat came as reinforcements from the Special Forces, accused of links to the Huthis and Saleh, were sent to the city of Taez, which is just 180 kilometres (110 miles) north of Aden and seen as a strategic entry point to Hadi's refuge.
"The bombings in Sanaa will now be taken as an excuse to open new fronts by attacking Taez and Marib (in the east)," said Yemeni youth activist Bassem al-Hakimi.