Activists say Syrian troops killed at least 59 people as they surged through a central town and parts of an eastern city, defying a UN request to stop the use of military force against civilians.
Sunday's fresh attacks on the town of Houleh in the Homs province and Deir el-Zour in the east are part of an ongoing campaign to quash protests demanding the resignation of President Bashar Assad.
The assaults come a day after UN Secretary General Ban Ki-Moon urged Assad, in a phone conservation, to end his regime's deadly crackdown.
More than 1,700 people have died in the last five months, with 300 of those dead in the past week, as government forces struggle to crush the anti-regime uprising, drawing strong international sanctions against Syria.
An exact death toll for the attacks on Sunday is not yet known.
Abdul-Karim Rihawi, the Damascus-based chief of the Syrian Human Rights League, says at least 42 people were killed in Deir el-Zour and 10 in Houleh.
The National Organization for Human Rights also cites 42 dead in Deir el-Zour but says the death toll in Houleh is actually 17. The group's spokesperson said 10 people were also shot Sunday in the city of Idlib while attending a funeral.
The rights groups say they anticipate Sunday's death toll will rise to almost 70.
Regions across Syria have witnessed passionate demonstrations against Assad since the uprising began in mid-March.
An activist in the city of Deir el-Zour told The Associated Press the military launched a pre-dawn raid on the city, attacking it from four sides and so far taking control of eight neighbourhoods.
"Human conditions in the city are very bad since it has been under siege for nine days," the activist said on condition of anonymity. "There is lack of medicine, baby formula, food stuff and gasoline. The city is totally paralyzed."
There are no exact numbers of the casualties, said the activist, adding that injured civilians can't be taken to hospitals and are being treated in homes and mosques that were turned into clinics.
The attacks in Houleh and Deir el-Zour came a day after Syria's foreign minister announced that free parliamentary elections would be held by the end of the year.
But Associated Press journalist Zeina Karam told Â鶹´«Ã½ Channel on Saturday that the announcement was unlikely to have much impact in Syria.
"The government has been making overtures and pledges of reform for several months now," she said from Beirut, Lebanon.
Assad's four-year term expired earlier this year. His government's crackdown on demonstrators has drawn broad international condemnation, particularly for its deadly siege on the city of Hama -- which is considered the uprising's epicenter.
Pope Benedict XVI joined a growing list of prominent figures denouncing Syrian violence on Sunday. During his weekly address, the pope called upon Syrian leaders to respond to what he said were "the legitimate aspirations of citizens."
Saudi Arabia's King Abdullah, whose country does not tolerate dissent, harshly criticized the Syrian government. He said on Sunday that he was recalling his ambassador in Damascus for consultations.
In late July, Prime Minister Stephen Harper issued a statement asking Assad to allow democratic reform or step aside. In the message he said it was "utterly indefensible" to use military force to suppress the Syrian people.
With files from The Associated Press and The Canadian Press
