A Syrian military official says government forces have repelled an attack by insurgents that was an attempt to break the siege imposed on rebel-held parts of the northern city of Aleppo.

And in nearby Idlib province, a helicopter gunship was shot down. That was reported by opposition activists.

Two activist groups — the Britain-based Syrian Observatory for Observatory and the Local Coordination Committees — say rebels shot down the helicopter over Idlib. It wasn't clear if the helicopter was Russian or Syrian.

Monday's developments come a day after Syrian rebels launched the offensive to break up the government's siege of eastern, rebel-held part of Aleppo.

Opposition activists say intense fighting still ongoing in Aleppo. The military official spoke on condition of anonymity in line with regulations. He did not elaborate.