Two civilians were killed Thursday as Syrian security forces moved into a district of the central city of Homs and a village in the northwest, the Syrian Observatory for Human Rights said.
The Britain-based rights group said one death occurred in the Homs district of Al-Nazihin, while shots were heard in Bab Sbaa and other areas of the volatile city.
The observatory also reported "one dead and five wounded in an assault by the army and security forces on the village of Al-Rama" in Idlib region.
It added that a girl of 10 had died of wounds received late Wednesday during shooting near police headquarters at Deir Ezzor in the east as she was travelling in a taxi with her family.
It said the security forces acted after mass demonstrations against President Bashar al-Assad's regime late Wednesday in numerous districts on Homs, including Bayyada, Al-Hamra, Bab Dreib and Bab Sbaa.
The United Nations says that more than 2,200 people have been killed since the beginning of near-daily popular protests against Assad's regime in mid-March.
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At Zabadani, 45 kilometres (28 miles) northwest of Damascus, six people were arrested by security forces who carried out searches, the Observatory added.
The Damascus suburb of Douma was cut off Thursday during the burial of a man shot dead at a checkpoint on Monday, it said.
The head of the Syrian League for the Defence of Human Rights, Abdel Karim Rihawi, said dozens of people had been arrested Wednesday at Qadam and Qabun in the Damascus region, and at Zabadani.
Other arrests occurred at Jizeh in the southern region of Daraa, at Hama in the centre and at Al-Jura and Quriyya, near Deir Ezzor.
Rihawi said demonstrations had taken place in the Damascus districts of Midan, Douma, Barzeh, Qadam and Qabun, as well as the towns of Harasta, Saqba, Hammuriyye, Keswa, Damir and Zabadani.
Other protests were held in Homs, Hama and Latakiya in the west, at Idlib in the northwest, Daraa, Qamishli in the northeast and at Deir Ezzor.
Assad's regime has defied western sanctions and blames "armed terrorist gangs" for the violence.