Saudi Arabia, Italy and Germany have shut down their embassies in Yemen amid growing political uncertainty as the country's UN envoy warned that the Arab world's poorest nation is at a crossroads between "civil war and disintegration".

The new closures come days after similar measures by the UK, US and France, threatening international isolation for a country that houses the world's most active al Qaida branch.

Yemen's elected president resigned last month after a power struggle with Shiite rebels, who have controlled the capital Sanaa since September.

The rebels, known as Houthis, have since dissolved the parliament, and president Abed Rabbo Mansour Hadi and his cabinet ministers remain under rebel house arrest.

United Nations negotiations to resolve the deadlock, headed by envoy Jamal Benomar, have stalled.

"Today Yemen is at a crossroads," Mr Benomar told a UN Security Council briefing yesterday. "Either the country will descend into civil war and disintegration, or the country will find a way to put the transition back on track."

The Italian Foreign Ministry said in a statement that the ambassador and his staff were returning to Italy, and expressed hopes that UN mediation would create conditions permitting the embassy to reopen.

In Berlin, Foreign Ministry spokeswoman Sawsan Chebli said its staff left the country today.

The Saudi embassy joined the rest of the Arab Gulf countries, which evacuated their embassies weeks ago, and a security official said that the Saudi ambassador and remaining staffers also left on Friday.

The Houthis, whose stronghold is in northern Yemen, are members of the Shiite Zaydi sect, which composes nearly 30% of the Yemeni population. Their takeover has emboldened the militant Sunni Muslims of Yemen's al Qaida branch, which has stepped up attacks in southern and central Yemen and garnered support among disgruntled Sunni tribes - raising concerns of a widening sectarian conflict.

Security officials today said a suicide car bomber struck a police headquarters in the central city of Bayda, which was recently captured by Shiite rebels. There was no immediate word on casualties.

No group claimed the attack but al Qaida has carried out dozens of similar attacks in Bayda province. In Radda, one of the largest cities in Bayda, battles have been raging between al Qaida and allied tribes against the Houthi rebels.

In the southern province of Shabwa, an al Qaida stronghold, security officials said gunmen suspected to be al Qaida militants attacked a main prison in Baihan and released five inmates after clashes with security guards.

Al Qaida militants seized an important army base of Yemen's 19th Infantry Brigade in the same region yesterday, following clashes with soldiers that left at least eight people dead while at least 15 soldiers were taken hostage before being later freed. Militants looted large amounts of weapons and transferred them to Marib, another al Qaida safe haven, officials said.

Al-Qaida in Yemen is considered by Washington to be the global terror organisation's most dangerous and active offshoot. Last month, it claimed the deadly attack on the Charlie Hebdo magazine in Paris.

The international withdrawal from Yemen comes as UN secretary-general Ban Ki-moon warned that the state is "collapsing before our eyes" as talks were under way on a draft Security Council resolution to address the crisis. Britain and Jordan were working on a resolution that British ambassador Mark Lyall Grant said would be ready "in the next few days".

A separate draft resolution by the Gulf Coordination Council strongly condemns the Houthis and their seizure of power and demands that they "immediately and unconditionally withdraw their forces from government institutions and from all regions under their control".

Saudi Arabia was a major economic lifeline for Yemen, but after the Houthi takeover of the capital in September, the oil-rich kingdom suspended its aid to Yemen, deepening fears of an economic collapse.