SANAA: Yemeni President Ali Abdullah Saleh said Saturday he would leave for the United States and give way to a successor, hours after his forces killed nine people demanding he be tried for killings of protesters over the past year.

But Saleh, who agreed to step down last month under a deal cut by his wealthier neighbours who fear civil war in Yemen will affect them, did not say when he would depart and vowed to play a political role again, this time opposed to a new government.

The bloodshed and political uncertainty hinted at the chaos which oil giant Saudi Arabia and Saleh's former backers in Washington fear Yemen could slip into, giving the country's al Qaeda wing a foothold overlooking oil shipping routes.

Troops from units led by Saleh's son and nephew opened fire with guns, tear gas and water cannon against demonstrators who approached his compound in the capital Sanaa after marching for days from the southern city of Taiz, chanting "No to immunity".

Mohammed al-Qubati, a doctor at a field hospital that has treated protesters during 11 months of mass demonstrations against Saleh, said some 90 people suffered gunshot wounds in addition to the nine killed. About 150 other people were wounded by tear gas canisters or incapacitated by gas, he said.

The marchers denounced the deal Saleh agreed last month giving him immunity from prosecution in exchange for handing power to his deputy, who is to work with an interim government including opposition parties before a February presidential election.

That plan, crafted by the Gulf Cooperation Council (GCC) and mirrored in the terms of a U.N. Security Council resolution, has been bitterly condemned by youth protesters who demand Saleh face trial and his inner circle be banned from holding power.

"The blood of the martyrs has been sold for dollars," shouted protesters, before forces from the Republican Guard and Central Security Forces attacked on roads leading to Saleh's compound, which was surrounded by tanks and armoured vehicles.

ACTIVISTS ROUNDED UP

Saleh, who repeatedly backed out of the Gulf plan to nudge him from power before a June assassination attempt forced him into hospital in Saudi Arabia, said he would both let Yemen's new government work, and oppose it.

Joe Stork, deputy Middle East director of Human Rights Watch, called on governments to ignore the immunity pledge and freeze Saleh's assets abroad, saying: "Promises of immunity encourage rather than deter illegal attacks."

Saleh said: "I will go to the United States. Not for treatment, because I'm fine, but to get away from attention, cameras, and allow the unity government to prepare properly for elections." He added that he would undergo some medical tests.

"I'll be there for several days, but I'll return because I won't leave my people and comrades who have been steadfast for 11 months," he said. "I'll withdraw from political work and go into the street as part of the opposition."

Alluding to the relationship of his poor, populous country to its resource-blessed neighbours, he said: "An unstable Yemen means an unstable region. So, protect the security, unity and stability of Yemen, neighbour states: its security is yours."

A Yemeni online publication quoted the U.S. ambassador in Sanaa, Gerald Feierstein, as describing the protest march as a provocative act, during a meeting with Yemeni journalists. The ambassador could not immediately be reached for comment.

As Saleh spoke, a member of the bloc of opposition parties that shares the cabinet with members of Saleh's party said security forces had rounded up dozens of people including Samia al-Aghbari, an activist in the anti-Saleh protest movement.

Aghbari sent a text message saying: "The Republican Guard is taking me and (another activist); they are dragging us by our clothes and shooting in the air."

Saleh's General People's Congress party said on Thursday that the protest violated the terms of the transition pact, under which the government is to oversee disengagement of Saleh's forces from rebel army units and tribal militias with whom they have fought in Sanaa and elsewhere.

Those battles, which the youth protesters regard as an internecine conflict among a criminal elite, have left parts of the capital and Taiz, 200 km (125 miles) to the south, in ruins and deepened a humanitarian crisis in a country with multiple, overlapping regional conflicts.

U.S. DRONE STRIKE IN SOUTH

Those include fighting with militant Islamists in the south, where Islamists have seized much of the territory in one province and have significant influence in another.

Saleh's opponents have accused him of ceding ground to Islamists to bolster his claim that he alone can check the Yemen-based branch of al Qaeda, which has planned abortive attacks abroad from Yemen.

A Yemeni security source said on Friday that a U.S. drone had killed a relative of the Qaeda wing's leader in Abyan, the Islamist militant-held province where battles with government troops have cost at least 50 lives this week.

A CIA drone strike killed Anwar al-Awlaki, a U.S. citizen linked to Al Qaeda in the Arabian Peninsula, earlier this year.

Fighting in Abyan has forced tens of thousands of people to flee the province, compounding the humanitarian crisis in a country where about half a million people are displaced and oil exports that fund imports of staple foodstuff have mostly ceased during the struggle over Saleh's fate.

Elsewhere in southern Yemen, gunmen killed a Briton of Yemeni origin and wounded a soldier with him in an attack on an oil company vehicle that a local official blamed on robbers.

In the southern port city of Aden, a grenade blast, apparently the work of feuding gangs, killed one person and wounded five at a market late on Friday, a local official said.

Separatist sentiment is running high in the south, formerly a socialist republic that fought a civil war with Saleh's north in 1994 after four turbulent years of formal union.