At least 20 antigovernment protesters were killed and many others injured when republican guards, central security forces and pro-regime armed groups broke into the freedom square in Yemen's Taiz province early on Monday.

The forces tried to disperse the sit-inners in Jamal St in downtown Taiz, but when they could not they set fire to tents and fired live bullets and teargas at thousands of people, who have been conducting a month-long sit-in to call for an immediate ouster of the regime..

Earlier, they surrounded the square from all entrances and the youth-led protesters fought back throwing rocks at patrols, tractors and heavy fire.

There were also gunmen on the roofs of some buildings near the square snipping protesters.

Furthermore, the forces besieged the field hospital at the square and many of those who were injured were left suffering without help, eyewitnesses said.

Meanwhile, many forces deployed to the streets and security is very tight.

Separately, jet fighters bombed earlier today areas in Abyan province after Islamic militants took over its capital Zunjbar.

Fierce battles are now continuing in the southern city, with more lives claimed and more injuries reported.