SANAA — Yemeni troops shot dead five demonstrators in the capital Sunday as they attempted to block a new bid by activists to bring 10 months of protests against veteran President Ali Abdullah Saleh to a head.

The defiant march by tens of thousands of pro-democracy demonstrators in Sanaa came despite the deaths of at least 12 people in a similar protest in the capital on Saturday.

Medical officials stationed at a makeshift field hospital near Change Square said three protesters and two dissident soldiers were killed, and at least 40 people wounded in Sunday's crackdown.

The violence erupted when protesters approached Al-Zubeiri Street, which marks the dividing line between parts of the capital held by troops loyal to Saleh and those held by dissident units led by General Ali Mohsen Al-Ahmar, who rallied to the opposition in March.

An AFP correspondent on the scene said snipers positioned on rooftops overlooking the street opened fire on the protesters, who were being led by dissident troops from Ahmar's First Armoured Division.

Ahmar's troops returned fire and fierce clashes ensued as unarmed protesters frantically dispersed.

Sunday's violence followed a similarly bloody day on Saturday when troops loyal to Saleh shot dead 12 protesters from a crowd of hundreds of thousands that marched on Al-Zubeiri Street.

Seventeen other people, at least five of them civilians, were killed in clashes that erupted between Saleh loyalists, and pro-opposition tribesmen and army units.

The pro-democracy activists, who have been demonstrating since January to bring an end to Saleh's 33-year rule, voiced defiance ahead of Sunday's march.

"We will continue with our protests... even if thousands of our youth are killed," said Walid al-Ammari, a spokesman for the protesters. "This is the only way to ensure the fall of the regime," he told AFP.

In a separate protest in Yemen's second-largest city Taez, one protester was killed when government troops opened fire on demonstrators also calling for Saleh's resignation.

Earlier Sunday, General Ahmar released a statement calling on the international community to take immediate action to stop the bloodshed and force Saleh to step down.

"We are calling for an urgent intervention by the international community to bring an immediate stop to the massacres by this ignorant murderer," the dissident commander said.

He said it was time for the international community to "force" Saleh to sign a deal brokered by impoverished Yemen's wealthy Gulf neighbours under which the president would transfer power to his deputy in return for a promise of immunity from prosecution.

Despite mounting pressure from Western governments as well as the six-nation Gulf Cooperation Council, Saleh has for months refused to sign the deal, even though he has repeatedly promised that he would.

After undergoing prolonged medical treatment in Saudi Arabia for blast wounds he sustained in a June bomb attack on his compound, Saleh has overseen an intensified crackdown on opposition to his rule since his surprise return in September.

The UN Security Council is currently drafting a resolution that will call on all sides to stop the violence, and for Saleh to sign the GCC agreement and step down.

But council members say it will not threaten sanctions.

In Sunday's statement, Ahmar called on all armed groups in the capital, including loyalist troops, armed tribesmen and his own dissident units, to withdraw to at least 200 kilometres (125 miles) from Sanaa.

But rival militiamen remained heavily deployed on the streets of the capital.