Syrian forces entered the town of Tafas near Deraa in the southwestern Hauran Plain today said, in a campaign aimed at crushing an anti-government uprising across the country.
Tanks and troops also stormed two main neighbourhoods in Homs overnight, human rights campaigners said, in the first incursion into residential areas in Syria's third city.
Machinegun fire and shelling was heard across the city of one million people, they said.
Protests, which began in Deraa on March 18th, erupted on Friday across Hauran, a strategic agricultural area bordering Jordan to the south and the Golan Heights to the west.
Protesters are demanding political freedoms, an end to corruption and that Syria's President Bashar al-Assad go. Mr Assad has said the protesters are part of a foreign conspiracy to cause sectarian strife.
Syrian authorities have blamed the nearly two months of violence on "armed terrorist groups" they say are operating in Deraa, Banias, Homs and other parts of the country, which has been ruled by the Assad family for the last 41 years.
Mr Assad's father, Hafez, who ruled for 30 years until his death in 2000, brutally suppressed an armed Islamist uprising in 1982 in which around 30,000 people were killed.
A human rights group says security forces have killed at least 800 civilians in the seven-week uprising.
At least eight tanks moved into the town of Tafas this morning. Residents said they heard gunfire and that army and forces broke into houses to arrest youths after occupying the centre of the town of 30,000 people.
Tanks also encircled the adjoining town of Dael near the main highway to Jordan as the army intensified its presence across the Hauran region having partly pulled out of Deraa this week and re-deployed in nearby rural towns, witnesses said.
"We knew they will not forgive us for our solidarity with Deraa. They are also targeting Tafas because it is harbouring lots of the youth who escaped the attack on Deraa," one of the residents said.
Tens of thousands of villagers from Hauran converged on Tafas on Friday and chanted slogans demanding Assad's overthrow.
Prevented from entering Deraa, still encircled by tanks after nearly two weeks, they staged one of the largest demonstrations in Hauran despite the heavy security presence in the plain, witnesses said.
In Banias on the Mediterranean coast, where rights campaigners said Syrian forces shot dead six civilians in an attack on Sunni districts yesterday, mass arrests continued.