Yemen moves closer to civil war as fighting intensifies

The fighting - led Yemen's largest tribe - poses the most significant challenge to Mr Saleh's rule after three months of street demonstrations and failed Arab mediation to ease him from office. Yemen's tribes command well-armed militias and can tap into traditional clan loyalties to possibly tips the scales against Mr Saleh's 32-year rule.

The Foreign Office last night said Britain was reducing staffing at its embassy in Yemen.

In a statement, Foreign Secretary William Hague said: "In light of the deteriorating situation, I have decided to reduce the staffing of our embassy to a level sufficient only to work on the most pressing and vital British national interests in Yemen, by temporarily removing four members of our staff."

Earlier this week, the escalating violence prompted the US State Department to order American diplomats and their families to leave the country.

Under Yemen's ancient codes, tribal leaders can declare that members follow their orders above all others. This potentially gives tribal chiefs the power to order government soldiers from their clans to stand down.

There was no apparent signals of mass defections from Mr Saleh's military, but some key commanders have moved over to the opposition.

The leader of Yemen's largest tribe, Sheik Sadeq al-Ahmar, warned Mr Saleh had the option to step down or be held accountable for "dragging the country to a civil war".

The battles broke out on Monday after an attempt by government forces to storm Mr al-Ahmar's compound in the capital, Sanaa. By yesterday, the clashes had widened to include areas around Sanaa's airport.

At least 109 people have been killed, including at least 28 yesterday, amid differing accounts on the explosion. The government said it was a blast at a weapons storage site. The opposition claimed military forces shelled a building used by tribal fighters loyal to Mr al-Ahmar and other major tribes who have joined him.

Mr al-Ahmar's tribe, the Hashid, turned against Mr Saleh two months ago, but had kept its militia on the sidelines. The current fighting, however, showed that the tribal fighters can hold their own against Mr Saleh's troops.

Mr Al-Ahmar's forces have laid siege to at least nine government ministries and government troops have responded with mortars and shelling.The targets yesterday included a TV station owned by Mr al-Ahmar, which was forced off the air.

Mr al-Ahmar urged neighbouring countries and other nations to boost pressure on Mr Saleh to cede power. He offered a ceasefire if Mr Saleh takes the first steps to halt the attacks.

But Yemeni authorities responded by escalating their campaign against Mr al-Ahmar with arrest warrants being issued against him and tribal leaders who represent the country's second- and third-largest clans.

It could be a risky gambit. In total, Mr al-Ahmar and his allies have tribal links to more than half the military and security forces. They would face a difficult test if tribal leaders invoked the traditional code of nakf - "the call" - which means to set aside other allegiances and follow the tribe's decisions.

Mr al-Ahmar said: "He (Saleh] is the one who started this war. They attacked us on our houses. We didn't start it.

"This man doesn't want anything good for Yemen."

Mr al-Ahmar also claimed that Mr Saleh intentionally triggered the current bloodshed in an attempt to portray his regime as the only option to avoid chaos.

"He wants to explode the situation. He is sending a message to the world, 'Look, if I leave this is the kind of war that will take place.'"

But Mr Saleh hasremained defiant. On Wednesday, he vowed he would not step down, nor allow Yemen to become a "failed state" and haven for al-Qaeda.

"I will not leave power and I will not leave Yemen," said a statement read by his spokesman. "I don't take orders from outside."