ISTANBUL — Violence rocked a wide portion of Syria on Saturday, with activists saying that about 100 people had been killed just days before a cease-fire that calls on the government to withdraw its heavy weaponry from cities and towns is to take effect.

Activists from Anadan, a town of about 40,000 just north of Aleppo, described the kind of government assault that seemed to be repeated around the country.

The Syrian Army had been shelling Anadan and villages nearby for about 72 hours without stopping. “They are following a torched-earth strategy,” said one activist, noting that the tanks have stayed outside the town but have not retreated. He insisted on anonymity because he wanted to return to the area.

Then scores of soldiers backed by thugs on the government payroll roared into the main square of the town on Friday and accosted a man, demanding that he point out the homes of the activists, said three activists interviewed on Saturday in the offices of the Syrian National Council, the main opposition group.