This article is more than 9 years old

This article is more than 9 years old

Security forces loyal to Yemen's president Ali Abdullah Saleh were locked in fierce gun battles on Tuesday in the capital Sana'a with guards from the country's most powerful tribal federation whose leader is backing protesters' demands for an end to the premier's 33-year rule.

At least 24 soldiers and 14 tribesmen were killed and 24 injured in the skirmishes, dimming the prospects for a negotiated solution to Yemen's political impasse.

The shootout, which pitted Saleh's central security forces against guards of Sadiq al-Ahmar, head of the Hashid tribal federation from which Saleh also hails, took place in sandbagged streets surrounding Ahmar's fortified compound, near several government ministries and the ruling party's headquarters.

Bullets fizzed through the air and plumes of black smoke rose from shattered houses as the two sides fired machine guns and shells at each other in a heavily–populated residential area in the east of the capital. A stray missile thudded into a mosque sending clouds of dust into the air and residents fleeing in panic.

As the fighting raged on into the evening, the opposition tribesmen began to advance, barricading main roads and sealing off several government buildings including the interior ministry. The estimated 500 tribal fighters are thought to be directing their assault from the Yemenia Airways office.

Local residents, most of whom have been evacuated from the area, say the violence was sparked "randomly" when Ahmar's guards tried to enter a primary school, claiming that Saleh's troops had been using it to stockpile weapons.

Others have accused Saleh, who recently backed away from signing a Saudi-led deal for his exit, of deliberately stirring the violence.

In a statement on Tuesday, Yemen's opposition members said that Saleh, who is facing mounting pressure from the west to quit office, was trying to spark a "civil war" in an attempt to remain in power.

"This is his [Saleh's] last resort," said Hassan Zaid, a leading opposition figure. "We're all praying that this doesn't escalate into a widespread conflict."

The government meanwhile has accused the Ahmar clan of "fomenting unrest" and "exploiting the current troubles in the country".

"The al-Ahmar sons and their gang turned away from the mediation effort and fired rockets and bullets heavily on government installations and citizens' homes," the defence ministry said in a statement.

Tribal mediators have been scrambling to bring about a swift end to the standoff but have so far been unsuccessful. Marib Press reported late on Tuesday that Ghalib al-Kamish, head of political security and the mediation committee, was severely wounded when a rocket hit Ahmar's house during a negotiation session.

It remains unclear what bearing the clashes will have on the protest movement. Protesters have expressed their concern that their peaceful movement may end up being eclipsed by the armed conflict.

"The violence will negatively affect the ongoing protest and will turn the dream of a peaceful revolution into a nightmare of a civil war," said Ibrahim Mothana, a 22-year-old Yemeni writer and activist.

"The protesters will stand firm to keep the uprising going and will never take a violent approach despite the ongoing conflict."

Saleh has resisted intense international pressure to step down. The British Foreign Office minister, Alistair Burt, issued a stinging rebuke, saying Saleh's refusal to sign an agreement under which he would leave office in 30 days in exchange for immunity from prosecution is "a matter of the deepest regret to the United Kingdom.

"Saleh is now isolated from leaders in his own party and the opposition who have demonstrated their commitment to a peaceful transition of power," he said.

The six-nation Gulf Co-operation Council, which has been mediating the negotiations, suspended its efforts indefinitely after Saleh's latest manoeuvre.