DARAA, Syria - Syrian security forces shot live ammunition and tear gas early Wednesday near a mosque where protesters have been camped out in southern Syria, killing six people including a paramedic, activists said.

The early morning attack near the al-Omari mosque in the southern city of Daraa marks the deadliest single day since anti-government protests inspired by uprisings across the Arab world reached this country last week. The latest deaths brings the number of people killed in Daraa since Friday to at least 13.

The weeklong standoff and violence in Daraa is remarkable in a country like Syria, where security is tightly controlled and state allegiance is expected. So far, the protests have been confined to Daraa and a few surrounding areas -- as well as small protests in the capital -- but that could rapidly change, particularly if the violence continues.

Groups on social networking sites have called for massive demonstrations across the country Friday, dubbed "Dignity Friday."

Telephone lies to Daraa were cut since the early morning hours, but an Associated Press reporter who arrived by mid-afternoon found a heavy security presence and most of the city's shops shuttered. Many checkpoints had been set up around the city, some manned by soldiers in camouflage uniforms, others by plain clothes security agents carrying rifles. Anti-Terrorism forces wearing dark blue uniforms were also out on the streets.

Very few people and cars ventured out, and sporadic cracks of gunfire could be heard coming from the old city, where most of the protests took place.

A witness who refused to give his name for fear of reprisals said hundreds of anti-terrorism forces were surrounding had surrounded al-Omari mosque. An ambulance was parked on the side of a road leading to the old city, part of its windshield smashed.

Nearby residents said heavy gunfire could be heard for about three hours starting shortly after midnight.

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 TV said.

An AP reporter saw an ambulance parked on the side of a road leading to the old city, part of its windshield smashed.

State TV showed footage of guns, AK47s, hand grenades and other ammunition as well as stashes of Syrian money which it said was seized from inside al-Omari mosque.

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 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 violence and are chasing those who were able to flee. The report didn't provide more details.

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.

Syria, a predominantly Sunni country ruled by minority Alawites, has been spared the wave of uprisings in the Middle East until now. Part of the reason is that the protesters know there will be a swift crackdown.

It is not clear why Daraa, a province of some 300,000 people near the Jordanian border, has become such a flashpoint for protests. The capital city -- also called Daraa -- is an agricultural hub that has suffered greatly from years of drought. It also is home to ultra-orthodox Sunni Muslims.

In 2006, security agents arrested 16 Syrians during a three-day sweep in Daraa province, accusing them of membership to the banned Muslim Brotherhood.

Last week's unrest started with the arrest by security forces of a group of students who had sprayed anti-government graffiti on walls in Daraa city, some 130 kilometres south of the capital Damascus.

Security troops trying to break up demonstrations calling for the students' release and for political freedoms killed seven people over several days.

So far, none of the slogans used by protesters have called for the ouster of President Bashar Assad, who took power in 2000 after the death of his father and predecessor, Hafez. Despite political repression and rights abuses, Assad remains relatively popular among some in the Arab world, in particular because he is seen as one of the few Arab leaders willing to stand up to Israel.

The demonstrators have been calling for reforms and political freedoms, and demanded the removal of the provincial governor, Faisal Kalthoum. Kalthoum was sacked Tuesday, but that failed to quell the protests.

On Wednesday, Abdul-Karim al-Rihawi, head of the Arab League for Human Rights, said several prominent activists have been arrested in the past two days, including well known writer Loay Hussein. Hussein had issued a statement calling for freedom of peaceful protests and expressed solidarity with the Daraa protesters.

Al-Rihawi said security agents picked up Hussein from his home in Damascus on Tuesday and confiscated his computer.

He said another activist, Issa al-Masalmi, was arrested in Daraa.

Also Wednesday, authorities said that six women who were detained last week after protesting in front of the Syrian Interior Ministry in central Damascus would be released Wednesday. The women were among 32 people, most of them relatives of political detainees in Syria, who were detained last Wednesday and charged by a prosecutor with hurting the state's image.

Al-Rihawi said the women would still have to stand trial despite their release.