"Two more civilians have been killed at Talbisa and a nearby village, taking the number of dead to seven" in the region, said the activist, who asked not to be named.
Earlier the activist said three people were killed in Talbisa and another two in nearby Rastan. More than 100 wounded were also taken to hospitals in Homs, a flashpoint of anti-regime protests.
Among those killed at Rastan were "a little girl called Hajar al-Khatib," he said.
Another activist, contacted by telephone from Nicosia, said several people were wounded as security forces unleashed "intense gunfire" in Rastan and Talbisa, after tanks sealed off both towns.
"Dozens of tanks at dawn encircled the towns of Rastan and Talbisa," the activist told AFP.
The towns are located between Homs, which is Syria's third-largest city, and Hama, on a stretch of highway north of Damascus that was cut off by tanks during the operation.
Security forces were carrying out searches in Talbisa, where a large crowd took to the streets on Friday for an anti-regime demonstration, said Rami Abdul Rahman, head of the London-based Syrian Observatory for Human Rights.
Also today, Syrian doctor and activist Mohammed Awad al- Ammar was charged with "damaging the prestige of the state and spreading false information," Abdul Rahman told AFP by phone.
The doctor, who works at a hospital near Daraa, a hotspot of the revolt, was arrested on April 29 shortly after meeting with a high-level military official to propose a "democratic solution" to Syria's political crisis, he said.