Saudi Arabia has evacuated diplomatic staff from Yemen following a Shi'ite Muslim Houthi militia's seizure of power there, joining Western countries who have also closed embassies due to fears of worsening violence.

The move reflected the hostility of Yemen's majority Sunni Muslim neighbours towards theIranian-backed Houthis.

Riyadh has suspended all work at its embassy in Yemen and evacuated its staff "due to the deterioration of the security and political situation", state news agency SPA reported on Friday, citing an official at the foreign ministry.

Germany and Italy also said on Friday they had closed their embassies in Yemen, following similar steps by Britain, France and the United States as the Houthis consolidated control after seizing the capital Sanaa in September.

A German Foreign Ministry spokeswoman said Berlin had shut down its mission on Thursday and staff left on Friday.

"In the past weeks the Houthis have seized power – this is unacceptably dangerous for us and could have consequences for the region," she said. "The situation is very concerning for us in Europe."

Italy also announced on Friday it had closed its embassy, citing a breakdown in security. It was withdrawing its ambassador and staff, the Foreign Ministry in Rome said.

Speaking from Sanaa, Julien Harneis, UNICEF representative in Yemen, said he was worried about "an economic crisis that is looming over the country".

"Yemen has been receiving a lot of assistance direct to the government from countries in the region, the Gulf states and Saudi Arabia," he told a news briefing.

"We are very worried that the political changes and the political crisis will make that less likely."

Al Qaeda-linked militants have stepped up attacks against Houthi fighters and U.N. Secretary-General Ban Ki-moon said on Thursday Yemen was "collapsing before our eyes" and slipping closer to outright civil war.

UN-backed negotiations on a political settlement continued in Sanaa on Friday. Thousands of Yemenis gathered after prayers in the mainly Sunni cities of Taaz, Ibb, al-Bayda and al-Hodeidah to denounce the Houthi takeover, witnesses said.

Top oil exporter Saudi Arabia along with other members of the Gulf Cooperation Council have accused the Houthis of staging a coup after they announced they were dissolving parliament and forming a new government last week.

Yemen has been in political limbo since the president and prime minister resigned last month after the Houthis seized the presidential palace.

Speaking from Sanaa, Julien Harneis, UNICEF representative in Yemen, said he was worried that Yemen was heading towards economic crisis.

"Yemen has been receiving a lot of assistance direct to the government from countries in the region, the Gulf states and Saudi Arabia," he told a news briefing.

"We are very worried that the political changes and the political crisis will make that less likely."

Al Qaeda-linked fighters seized an army base in a dawn attack in the southern province of Shabwa on Thursday.

In response, tribal fighters took over two other army barracks in Shabwa on Friday to prevent al Qaeda seizing more weapons and avoid a Houthi attack on the south, tribal sources told Reuters.