Numerous casualties have been reported in the Yemeni capital, Sanaa, after troops loyal to President Ali Abdullah Saleh opened fire on antigovernment protesters.
Medical officials say between four and 13 people were killed as a result of the violence and dozens other wounded.
Witnesses said snipers located on rooftops opened fire on the crowd of tens of thousands of protesters calling for the president to step down.
The latest violence comes a day after security forces fired on a massive rally of some 300,000 people in Sanaa, killing at least 12 protesters and wounding some 300.
Nearly 1,500 people have been killed in clashes since the start of antigovernment protests in Yemen in February.
compiled from agency reports