BEIRUT, (AP) — Activists are reporting heavy fighting in Syria’s largest city as battles intensify ahead of a visit by the new international peace envoy.

The Britain-based Syrian Observatory for Human Rights and the Local Coordination Committees say the fighting Wednesday was mostly near the government-held Aleppo International Airport.

Aleppo-based activist Mohammed al-Hassan says the airport, which includes a military base, is widely used by the regime to bomb rebel-held areas in Aleppo.

Diplomatic efforts have so far failed to stop the bloodshed in Syria, but the new U.N.-Arab League envoy Lakhdar Brahimi plans to travel to the country this week in a bid to revive them.

U.N. Secretary-General Ban Ki-moon said Brahimi will sit down with President Bashar Assad during an upcoming visit, although the date has not been announced.