Yemeni security forces opened fire Sunday on anti-governmentprotesters marching through the capital killing at least four people, a medicalofficial said.
Mohammed al-Qubati, the director of a field hospital atSanaa's main protest site dubbed "Change Square", also said at least37 people were wounded in the violence.
Witnesses said snipers on rooftops opened fire on the crowdof tens of thousands of protesters, marching through the streets to call forthe resignation of President Ali Abdullah Saleh.Loyalist forces of the Republican Guard, a unit led bySaleh's son Ahmed, also lobbed tear gas at the demonstrators.
Witnesses said that the Republican Guard clashed near ChangeSquare with the anti-government troops of renegade army general Ali Mohsenal-Ahmar, who defected and joined protests months ago.
Pro-Saleh security forces also tried Sunday to disperse alarge protest in the southern Yemeni city of Taiz, killing one woman andinjuring seven others, medical officials there said.
Sunday's violence comes a day after security forces fired ona massive rally of some 300,000 people in Sanaa, killing at least 12 protestersand wounding some 300.
"No immunity, no guarantees. Saleh and his aides mustbe prosecuted," chanted protesters in Sanaa. "Free people of theworld, Saleh must be tried."
President Saleh clings to power in the face of more thannine months of massive street protests, inspired by popular uprisings inTunisia and Egypt.
Saleh, who has been in office for 33 years, has staunchlyrefused to quit power.
He has balked at signing a deal that the United States andSaudi Arabia have backed in hopes of providing a smooth transition of power.Under the agreement, Saleh would resign and hand power to his vice president inreturn for immunity from prosecution.