New clashes erupted Tuesday, March 12 in an intensifying battle for control over Aleppo's international airport and nearby military bases in Syria's north, activists said, according to AP.

Rebels have tried for weeks to capture Aleppo's international airport and nearby air bases as part of their campaign to erode the regime's air supremacy in the 2-year-old conflict that the United Nations says has claimed more than 70,000 lives.

Rebels have made significant strategic advances in the north in the past months, capturing military bases, two dams on the Euphrates river and the city of Raqqa in the northwest — the first urban area to fall into opposition hands since the uprising against Assad's regime began in March 2011.

The rebels also control large swathes of land outside of Aleppo. The battle for the city itself, Syria's main commercial hub, is locked in a stalemate. Rebels pushed into the city in July and captured several neighborhoods and it has been a major battleground in the civil war ever since.

The army still holds large parts of Aleppo and maintains control over the airport, the country's second largest. Crucially, Syria's air space is firmly controlled by the regime in Damascus, which uses its warplanes to regularly bomb rebel strongholds.

The Syrian Observatory for Human Rights said clashes erupted anew on Tuesday around the airport and rebels also intensified their assault on the Nairab and Mannagh air bases near the strategic facility, which has not been handling fights for weeks because of the fighting.

There were also intense clashes at another nearby airfield known as Kweiras, according to the Observatory, a Britain-based anti-regime group that relies on a network of activists on the ground.