Three Syrian government soldiers have been killed in clashes with rebels in the central province of Homs, an activist group said.
The UK-based Syrian Observatory for Human Rights said the clashes broke out when government forces tried to enter the town of Rastan.
The group also reported fresh clashes in Deir el-Zour province, along the Iraqi border.
The fighting comes a day after Syria formally accepted a plan by UN-Arab League envoy Kofi Annan to end the year-old conflict that the UN says has killed more than 9,000 people.
The plan calls for a ceasefire to allow for dialogue on a political solution.
Western countries have called on president Bashar Assad to back his commitment with action. The opposition accuses him of stalling for time.