SANAA (Reuters) - At least 26 people were shot dead and hundreds wounded on Sunday when security forces fired on demonstrators who charged police lines in Yemen's capital Sanaa, in a dramatic escalation of protests against President Ali Abdullah Saleh.
Gunfire and explosions were heard late into the night and protesters vowed to continue demonstrations on Monday morning. A Reuters witness earlier saw security forces fire at protesters from buildings and use water cannon and tear gas to hold back tens of thousands of demonstrators.
Some of the protesters were wielding batons or throwing petrol bombs at police cars.
"Why are you still sitting here? Get moving everyone, move. Go defend the martyrs' honor," blared a voice on loudspeakers in Change Square, where thousands have camped out in tents for eight months to demand an end to Saleh's 33-year rule.
Hundreds still in the ramshackle camp answered the call, running and chanting "God is great, freedom!" as they streamed down the street.
"This is the worst day I've seen in three months. We're expecting more dead to come in," said doctor Jamal al-Hamdani, who was treating dozens of patients with bullet wounds.
The injured were rushed in on stretchers and laid out on blood-streaked floors in a mosque being used as a makeshift hospital.
Medics there estimated some 342 had suffered gunshot wounds, with 36 in a critical condition.
The face of one dead man was torn away from an injury medics said appeared to be caused by a rocket-propelled grenade (RPG) fired at his head.
Frustrated by their failure to oust Saleh, who is clinging to power as he recovers in neighboring Saudi Arabia from a June assassination attempt, protesters were keen to ratchet up demonstrations.
"Escalation, escalation," they chanted, running past large numbers of police loyal to Saleh.
Soldiers from an army unit that has defected to support the protests cautiously pointed machine guns and RPGs out from behind sand-bagged street corners.
The bodies of some protesters killed during the demonstrations were returned to Change Square covered in white sheets, their names and date of death scribbled on a sheet of paper over their chest.
Tawfiq, 23, wiped away tears as he cradled the head of his 33-year-old cousin, who died from a gunshot to his stomach.
"We protested and camped here together since the beginning," he said, surrounded by sobbing mourners lifting their arms to the sky. "I turned around and saw him fall. I tried to hold together the wound. I can't bring myself to call his parents."
Witnesses said protesters had seized a road junction near the site of the clashes. The area had marked part of the dividing line between the districts of Sanaa held by troops loyal to Saleh and those taken by general Ali Mohsen, who defected and threw his weight behind protesters months ago.
Cheering protesters said they would add more tents along the junction for their sit-in.
PROTESTERS APPEAL TO U.N.
After a long period of relative quiet, protest organizers had planned to escalate demonstrations this week after a long period of relative quiet. Some told Reuters they had anticipated the march would spark a surge in violence.
Yemeni politicians had expressed optimism in recent days that a power transition deal, thrice rejected by Saleh, would soon be signed in his name by the vice president.
Sunday's unrest may unsettle any political progress.
"The unlicensed marches that happened today have caused escalation and preemptively foiled dialogue," Muttahar al-Masri, Yemen's interior minister said.
The opposition sought international condemnation.
"This massacre will not pass without punishment ... we call on the United Nations to end its silence and take decisions to protect the Yemeni people," the National Council, a body formed by protesters, said in a statement.
The ruling party blamed gunmen belonging to opposition parties for opening fire on the march. Witnesses reported government forces and troops from General Mohsen exchanged fire.
In a statement aired on Yemeni opposition channel Suhail TV, his forces called the shooting at protesters a "crime against humanity" and appealed to wealthy Gulf Arab neighbors for help.
Local diplomats have grown increasingly worried the two sides could descend into more serious military confrontation.
Tensions have been simmering in Sanaa recently, with heavy shelling and gun battles in some neighborhoods. Earlier on Sunday, fighting broke out in a northern district of Sanaa, the latest breach of a ceasefire between the tribesmen troops loyal to Saleh.
The United States and Saudi Arabia fear rising turmoil in Yemen will embolden al Qaeda's Yemen-based regional wing to launch strikes in the region and beyond.
But protesters, electrified by Sunday's events, said they would not back down.
"The bullet, the pain, are not a problem. We need to get rid of the regime," said Radwan Qasim, 37, as he nursed a gunshot wound on his leg. "We'll go on until they kill us all if we have to."
(Additional reporting by Mohammed Ghobari and Khaled al-Mahdy; Writing by Erika Solomon and Isabel Coles; Editing by Sophie Hares)