Fierce clashes erupted in Yemen's second city Saturday as protesters in the capital Sanaa condemned international silence in the face of a government crackdown that left more than 15 dead the previous day.
"Oh world, the children and women of Taez are being killed...where is your conscience?" chanted tens of thousands of protesters in Sanaa who for 10 months now have been calling for President Ali Abdullah Saleh to step down.
"To the world and the (UN) Security Council, don't you see Saleh is shelling Taez?" they chanted.
On Friday, government forces shelled a protest site in the flashpoint city of Taez, south of the capital, killing 15 civilians, including at least three women and three children, medics said.
Friday's violence, which also left at least 40 people wounded, erupted when security forces loyal to Saleh began shelling areas around Freedom Square, the epicentre of the protest movement in Taez.
Witnesses blamed the violence on the Republican Guard, an elite unit commanded by Saleh's son Ahmed, accusing it of firing tank and artillery rounds into a crowd of protesting civilians.
The violence continued Saturday as armed tribesmen who have thrown their support behind the protest movement clashed with government troops in the Hassab district of Taez, witnesses said.
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There were no immediate reports of casualties.
Youth activists called for a general strike in the city as thousands took to the streets to condemn Friday's bloodshed. Residents said most businesses were closed.
The escalation of violence came as UN envoy Jamal Benomar returned to Yemen for a new push to end the 10-month crisis.
Benomar arrived in Sanaa on Thursday and began meeting with government and opposition officials to discuss a roadmap for implementing a Gulf peace plan which would see Saleh step down in return for a promise of immunity from prosecution for himself and his family.
Saleh, who has been in power in Sanaa for 33 years, has so far failed to sign up to the blueprint despite repeated promises that he would.
On Saturday, an opposition spokesman said the assault on Taez is "proof" he has no intention to resign.
"Saleh totally rejects the initiative... and proof of this is what is happening to the peaceful protesters in Taez," said Mohammed Qahtan, spokesman for the Common Forum parliamentary opposition bloc.
The government's crackdown left hundreds dead and thousands wounded since January.