Shelling and automatic gunfire Wednesday rocked the city of Homs, a hub of anti-regime protests in central Syria, a human rights activist said.

"Shelling and automatic gunfire could be heard early Wednesday in the (Homs) neighbourhood of Bab Amr and in nearby villages, Mashada, Jobar and Sultanya," Najati Tayara told AFP.

He said that the villages, with a combined population of some 100,000 inhabitants -- many of them Bedouins -- have been the target of a security operation since Monday.

The Syrian army had swept the agricultural area searching for weapons and spreading fear among the population, he said.

"This operation terrified residents and security agents took part in looting," Tayara said.

He added that 50 tanks had rolled into the Homs neighbourhood of Sittin on Wednesday.

"Checkpoints were in place at the entrances of Homs," he added.

The army first moved into Homs on Friday and tanks rumbled into opposition pockets of the industrial city overnight Saturday-Sunday, activists said.