Fresh violence in a southern Syrian city has left as many as six people dead today, according to activists.

This would make it the deadliest single day since anti-government protests inspired by uprisings across the Arab world reached Syria last week.

The six were reportedly killed in the southern city of Daraa when security forces launched an attack near the al-Omari Mosque, where anti-government demonstrators have taken shelter. The activist said that a paramedic was among the dead.

Syria's state-run TV reported that four people died when "an armed gang" attacked an ambulance in Daraa. The dead included a doctor, a paramedic, a driver and a policeman.

The conflicting information and the discrepancy in the toll of the dead could not be immediately reconciled. The latest attack is likely to raise tension in Daraa as security forces are now expected to intensify their crackdown on anti-government activists.

The Syrian government has sought to contain the first serious intrusion of the Arab world's political unrest by firing the governor of the southern province of Daraa, where security forces killed seven protesters in the main city of Daraa over the weekend.

But the dismissal failed to quell popular anger and the protests reached the province's village of Nawa, where hundreds of people marched demanding reforms on Tuesday, activist said.

The TV said security forces were able "to kill and wound" some of the attackers in Wednesday's incident and are chasing those who were able to flee.

A video posted on Facebook by activists showed an empty street, purported to be near al-Omari Mosque as shooting could be heard in the darkness. In the footage, a voice is heard shouting: "My brother, does anyone kill his people? You are our brothers."

The authenticity of the videos could not be independently verified.

State TV denied that security forces had stormed the mosque.