"We know for a fact that the opposition does have heavy weapons," UN Under-Secretary-General for Peacekeeping Operations Herve Ladsous told reporters. He gave no details on where the arms had come from, but said such weaponry included tanks and armored personnel carriers.
UN officials and diplomats say the rebels have been capturing weapons from Syrian soldiers they have overrun in parts of the country where they have gained an upper hand.
Ladsous said he had no proof the rebels had used heavy weapons against the army, which Syrian President Bashar al-Assad has deployed for 17 months against an increasingly militarized opposition determined to oust him.
In Syria on Thursday, the fight intensified for Aleppo, the country's second city, as rebels turned the gun of a captured tank against government forces, shelling a military airbase north of the city.