The Syrian government ordered more tanks into Deraa on Saturday and heavy gunfire was heard in the city as security forces tried to crush a revolt against President Bashar Al-Assad, residents said.

Syrian troops and tanks first swept into Deraa on Monday to quell pro-democracy protests against Assad that have spread across the country of 20 million, posing the biggest challenge to his rule and prompting Western powers to impose sanctions.

Deraa, a southern city of 120,000 people, is the cradle of a six-week-old uprising which started with demands for more freedom and an end to corruption. It developed into a movement to overthrow Assad following a violent crackdown by authorities.

Residents said they could hear heavy gunfire, mostly from Deraa's old quarter, which is situated on a hill near the Jordanian border and is mostly residential.

"Since dawn, we've been hearing a heavy exchange of gunfire that is echoing across the city and you do not know what's happening," Abu Tareq, a resident, told Reuters by phone. "I saw more than 15 tanks that had entered from the Damascus highway heading in the direction of the Old City."

It was not immediately clear whether tanks and mounted armoured carriers were shelling the city or agricultural land near the border.

Another resident, Abu Ahmad, told Reuters he had heard tanks had stormed areas in the old city, where the Omari Mosque, which has been a focal point for protests, is located.

"It looks like they (security forces) want to finish their campaign today. From the new tank deployments, it looks as though they are intensifying their operations today."     Despite the heavy military deployments and mass arrests, demonstrators again took to the streets calling for Assad's overthrow on Friday.

Soldiers in Deraa killed 19 people on Friday when they fired on protesters who were trying to enter the city from nearby villages in a show of solidarity, a medical source said.

Syrian rights groups put Friday's death toll at 62, pushing the number of deaths since an uprising that has posed the biggest challenge to the Assad dynasty's four decades in power, to more than 500.

The crackdown prompted Western powers to take their first concrete steps in punishing Syria for the bloodshed. Washington imposed new sanctions on government figures, including Assad's brother, who commands the army division which stormed Deraa on Monday.

Assad's cousin, Atif Najib, was also targeted as was Ali Mamluk, director of general intelligence and Iran's powerful Revolutionary Guard, accused of helping the Syrian crackdown. Syria has denied Iran was helping it quell protests.

European Union diplomats said they had reached preliminary agreement to impose an arms embargo on Syria and would urgently consider further measures.

Syria blames armed terrorist groups

More demonstrations flared on Friday in the central cities of Homs and Hama, Banias on the Mediterranean coast, Qamishly in the east, Harasta, a Damascus suburb, and the capital itself.

Syrian rights group Sawasiah said this week at least 500 civilians had been killed since the unrest broke out.

Authorities dispute that, saying 78 security forces and 70 civilians died in violence they blame on armed groups.

State news agency SANA said on Friday "armed terrorist groups" had killed eight soldiers near Deraa. It said groups had opened fire on the homes of soldiers in two towns near Deraa and were repelled by guards.

But a witness in Deraa said Syrian forces fired live rounds at thousands of villagers who descended on the besieged city.

A rights campaigner in Deraa said on Friday makeshift morgues in the city contained the bodies of 85 people he said had been killed since the army stormed the city on Monday.

Residents say a humanitarian crisis is growing.

The repression has brought condemnation from Western powers which for several years had sought to engage Damascus and loosen its anti-Israel alliances with Iran and the militant groups Hezbollah and Hamas. – Reuters