At least 41 civilians including seven children were shot dead on Friday by Syrian security forces in the capital Damascus and the restive central city of Homs, the Syrian Observatory for Human Rights said.
It said in a statement on Saturday that 12 people -- among them two children aged 10 and 12 -- were killed in Homs and that a 14-year-old boy was killed in Aqrab village in the Homs area where the opposition charges the regime is planning a massacre.
To the north, the Britain-based rights watchdog said five civilians were shot dead by security forces in the city of Hama, a focal point of dissent against the regime of President Bashar Al-Assad.
In Damascus province, 18 civilians including two children were shot dead in Duma, Saqba, Kafarbatna, Hamourieh and Dmeir.
The Observatory said that in the southern province of Daraa, cradle of the revolt that erupted in mid-March, a woman and a young girl were killed.
And near the Turkish frontier in the north, in Idlib province, two civilians including a 15-year-old youth were killed in Maaret Numan town, and a taxi driver was shot dead in the same area.
The United Nations estimates that at least 4,000 civilians have been killed in Syria in the past nine months.
On Friday, the opposition Syrian National Council warned of a looming bloody final assault on Homs using the pretext of what the regime called a "terrorist" attack on an oil pipeline on Thursday.
"The regime (is) paving the way to commit a massacre in order to extinguish the revolution in Homs," said the SNC, a coalition of Assad opponents.
Homs, an important central junction city of 1.6 million residents divided along confessional lines, is a tinderbox of sectarian tensions that the SNC said the regime was trying to exploit.