In the eastern city of Deir Ezzor, where security forces were carrying out operations in nearly all neighbourhoods, two civilians were shot dead tonight, said Rami Abdel Rahman, head of the Syria Observatory for Human Rights.
Afterwards, some 3,000 people gathered in front of the house of the new governor, Samir Othman al-Sheikh, to "demand an end to the killing," he said.
Earlier, residents were out in the streets trying to prevent security forces carrying out arrests, he said.
In Qatana, 25 kilometres south of Damascus, security forces armed with machine guns and other weapons arrived in the town in pickup trucks overnight and carried out the arrests before searching for more protesters.
The sweep came as people took to the streets of Damascus and Qatana to protest after security forces killed 11 people on Wednesday in Kanaker, 50 kilometres southwest of the capital, said human rights activists.