The Syrian government has sent troops backed by tanks into rebellious areas, hunting down activists and torching their homes and bulldozing others, opposition groups said.
At the United Nations, international envoy Kofi Annan set an April 10 deadline for full compliance with a peace plan to end the violence in Syria.
He also told the Security Council at a closed door briefing that Damascus has agreed to withdraw its troops from cities by that date, reversing its previous refusal to implement the measure, diplomats said.
The opposition is deeply sceptical of President Bashar Assad's intention to abide by his promises, describing it as another attempt to buy time while government troops continue their assault on the rebels.
Several times over the past few months, the Assad regime has agreed to a peace plan, only to ignore it on the ground.
Most recently, it signed on to a plan by Mr Annan, but then rejected his appeal for the government to lay down its weapons before the rebels did.
Also, several months ago Syria accepted an Arab League plan to send monitors to work for a ceasefire, but the mission collapsed in violence.
Activists said fierce clashes were taking place in the central region of Homs, after which rebels took control of the national hospital in the Jouret al-Shayah district.
Human rights groups and the opposition have accused government forces of abusing and torturing wounded activists in the hospital in previous months.
The Local Co-ordination Committees and the British-based Syrian Observatory for Human Rights said rebels found around 70 unidentified bodies in the hospital refrigerators, apparently belonging to people killed in earlier fighting.
In the south, dozens of tanks surrounded the town of Dael early yesterday before troops pushed in, shooting holes in rooftop water tanks and targeting dozens of activists' houses, torching some and bulldozing others, said local activist Adel al-Omari.
"They focused on the activists. They have their names and have been tracking them," Mr al-Omari said, speaking by telephone from a garden in Dael where he was hiding.
"They went in and spread fuel to totally burn them down."
Activists said government troops also set fire to homes in the north western village of Haas, where one activist said they killed seven people in one house.
"The regime forces have pretty much stopped arresting people," activist Fadi al-Yassin said via Skype. "They either kill them right away or keep them for one day to get information and then kill them."