Syrian troops have launched assaults on several towns around the country including two near the largest city of Aleppo, according to activists.
The latest violence comes despite Syrian president Bashar Assad's agreement to implement a ceasefire starting on April 10.
The UK-based Syrian Observatory for Human Rights said troops are clashing with rebel army defectors in the northern towns of Hraytan and Anadan near Aleppo.
The Observatory also reported fighting in the Damascus suburb of Douma and the southern village of Kfar Shams.
The truce is the keystone of a plan put forward by Kofi Annan, the joint UN-Arab League envoy, aimed at ending the country's year-long crisis.