BEIRUT (AP) — Syrian activists say the battle between rebels and government troops for the country’s second-largest airport is intensifying.

The director of the Britain-based Observatory for Human Rights, Rami Abdul-Rahman, says the fighting Saturday near Aleppo International airport is concentrated around a section of a highway connecting the city with a strategic facility the rebels have been trying to capture for weeks.

Rebels have recently taken control of two military bases protecting the airport. They have also cut off a highway the army has been using to transport troops and supplies there.

President Bashar Assad’s troops have been locked in a stalemate with the rebels in Aleppo since July, when Syria’s largest city became a major battlefield in the nearly two-year conflict.