Syrian troops shelled and raided opposition strongholds and clashed with rebel fighters around the country on Saturday, killing at least two people, activists said dpa reported.
The heavy fighting focused on the villages of Sermin and Khan Sheikhoun, in the northern province of Idlib, forcing local rebels to retreat from both areas, activists said.
The state news agency SANA reported that "several terrorists" were killed in Idlib, which is located near the Turkish border.
Government forces also bombed towns near the capital Damascus following overnight clashes with rebels. A video posted on Syrian opposition websites showed members of the Free Syrian Army announcing that defectors of various brigades had arrived in the area to help rebels "confront the tyrant regime."
A Syrian helicopter pilot who refused to obey orders to bomb the area of Azaz in Aleppo, targeted a Syrian security intelligence headquarter instead before fleeing to Turkey, the Dubai-based broadcaster Al Arabiya reported, quoting opposition sources.
If confirmed, this would be the first incident of its kind in the one-year unrest. News from Syria is difficult to verify independently as the government has barred most foreign media from restive areas since the pro-democracy uprising started in March 2011.
The violence continued as UN-Arab League envoy Kofi Annan was set to travel to Moscow and Beijing at the weekend as part of his efforts to end the violent conflict in Syria.
A western diplomat based in Beirut told dpa that "the negotiations with the Syrian authorities and the UN-Arab league envoy have reached a critical stage and talks in Russia and China are needed to exert pressure on the Syrian regime."
Russia and China, the main allies of President Bashar al-Assad, have so far blocked binding resolutions on Syria at the UN Security Council.