Activists are reporting the heaviest fighting in months in the northern Syrian city of Aleppo.

The Britain-based Syrian Observatory for Human Rights says the clashes concentrated in the eastern neighborhood of Sakhour.

The opposition's Aleppo Media Center said troops failed to advance in the battle that continued until the early hours of Friday.

The fighting follows three U.S. officials saying Thursday that President Barack Obama has authorized sending weapons to Syrian rebels for the first time.

The attack on rebel-held Sakhour comes a week after Syrian government forces backed by Hezbollah fighters captured the town of Qusair near the Lebanon border.

Building on its victory in Qusair, the Syrian military is trying to try to clear rebel-held areas in the central provinces of Homs and Aleppo.