Also Wednesday, activists said rebels were attacking the Wadi Deif military base in the northern province of Idlib. The base, which is near the strategic town of Maaret al-Numan, has been under siege for weeks.
In October, rebels captured Maaret al-Numan, a town on the highway that links the capital Damascus with Aleppo, Syria's largest city and a major battleground in the civil war since July.
The attack on Wadi Deif comes a day after rebels captured the town of Harem near the Turkish border. The rebels have captured wide areas and military posts in northern Syria over the past weeks.
In Lebanon, airport officials in Beirut said Syria's Deputy Foreign Minister Faisal Mekdad and Assistant Foreign Minister Ahmad Arnous flew early Wednesday to Moscow.
Their visit to Moscow comes two days after Assad met in Damascus with Lakhdar Brahimi, the international envoy to Syria. Brahimi, who is scheduled to go to Moscow as well, gave no indication of progress toward a negotiated solution for the civil war.
Brahimi is still in Syria and met Tuesday with representatives of the opposition National Coordination Body, state-run news agency SANA said. The head of the group, Hassan Abdul-Azim, said Brahimi briefed them on his efforts to reach an "international consensus, especially between Russia and the United Stated to reach a solution."
NCB spokesman Rajaa al-Naser said his group said there must be an end to violence and formation of a "transitional government with full prerogatives."