Britain reportedly has withdrawn its remaining special forces from Yemen, days after a similar U.S. move, in response to the worsening security that the U.N. envoy for Yemen described as the "edge of civil war."

The reported development comes as Yemeni Foreign Minister Riyadh Yaseen called on his Arab neighbors to intervene militarily to stop the inroads made by Shiite Houthi fighters in the predominantly Sunni Muslim country.

Reuters, quoting a person familiar with the matter, reported on the U.K.'s withdrawal of its special forces. Britain withdrew staff from its embassy in Sanaa last month and suspended operations because of the deteriorating security situation there.

The U.S. Embassy suspended operations last month for the same reasons, and Saturday the State Department said "the U.S. Government has temporarily relocated its remaining personnel out of Yemen." The Associated Press reported over the weekend that U.S. military forces, including Special Forces commandos, evacuated the Al Anad air base near the southern city of al-Houta, which was seized by al-Qaida in the Arabian Peninsula.

But The New York Times reported that "[e]ven after the withdrawal of American troops, the Central Intelligence Agency will still maintain some covert Yemeni agents in the country. Armed drones will carry out some airstrikes from bases in nearby Saudi Arabia or Djibouti in the Horn of Africa, as was done most recently on Feb. 20. Spy satellites will still lurk overhead and eavesdropping planes will try to suck up electronic communications."

Yaseen, the Yemeni foreign minister, urged his Gulf state neighbors for help against the gains made by the Houthi rebels.

"We have addressed both the [Gulf Cooperation Council] and the U.N. for the need of [imposing] a no-fly zone and banning the use of warplanes at the airports controlled by the Houthis," he told al-Sharq al-Awsat, the pan-Arab newspaper.

The unrest in Yemen began earlier this year when the Houthis, who follow a strain of Shiite Islam, took control of Sanaa, the capital, and subsequently dissolved Parliament and seized power. The Houthi movement, which began in 2004, wants greater autonomy for the north of Yemen. Its members are avowedly anti-U.S., but are also battling al-Qaida in the Arabian Peninsula, regarded as the most successful al-Qaida franchise. They are also likely to take on the self-described Islamic State, which last Friday claimed responsibility for bomb attacks on two mosques in Sanaa frequented by Houthi supporters; 139 people were killed. Both AQAP and ISIS are Sunni and regard Shiites as heretics.

Add to this mix regional rivalries. The overwhelming majority of the Gulf states — and indeed the wider Muslim world — is Sunni. Iran, however, is Shiite, and is seen as backing the Houthis. This greatly worries the region's Sunni powers, primarily Saudi Arabia, who are already watching with alarm Iran's increasing influence in Iraq as well as Tehran's negotiations with the West over its nuclear program.

Jamal Benomar, the U.N. special envoy for Yemen, told an emergency meeting of the U.N. Security Council on Sunday that the country had been pushed "towards the edge of civil war."

"Following the suicide bombings and fighting, emotions are running extremely high, and unless a solution can be found in the coming days the country will slide into further violent conflict and fragmentation," he said.

The U.S. has played a key role in Yemen, carrying out drone strikes against al-Qaida members in Yemen. Just last September, President Obama cited Yemen (along with Somalia) as a successful example of America's counterterrorism strategy. Five months later, that seems an unlikely example.

The Washington Post reported last week that the Pentagon can't account for more than $500 million in military aid to Yemen, "amid fears that the weaponry, aircraft and equipment is at risk of being seized by Iranian-backed rebels or al-Qaida." And The Times reported Monday: "The loss of Yemen as a base for American counterterrorism training, advising and intelligence-gathering carries major implications not just there, but throughout a region that officials say poses the most grievous threat to United States global interests and to the country itself."

NPR