Human Rights Watch issued a 38-page report detailing raids it said amounted to war crimes conducted while international envoy Kofi Annan was negotiating an April 12 cease-fire, CNN reported.
In the latest clashes at least 27 people died Wednesday in Aleppo and Damascus Countryside provinces, the Syrian Observatory for Human Rights said.
The Human Rights Watch report tells of executions, killings, property destruction, arbitrary detentions and torture.
"While diplomats argued over details of Annan's peace plan, Syrian tanks and helicopters attacked one town in Idlib after another," said Anna Neistat of Human Rights Watch. "It was as if the Syrian government used every minute before the cease-fire to cause harm."
The Human Rights report is based on a field investigation in the towns of Taftanaz, Saraqeb, Sarmeen, Kelly and Hazano in Idlib governorate.
Neistat warned peace efforts "will be seriously undermined if abuses continue."