BEIRUT – Intense clashes between the Syrian army and rebel fighters near the country's second-largest airport killed about 150 people in recent days, anti-regime activists said Friday, pointing to the significance both sides in the country's civil war place on controlling key infrastructure.

The battle for the international airport near Aleppo, Syria's largest city, resembles other battles over strategic assets that could provide an edge in the larger fight for the country.

This week, rebels seized a hydroelectric dam and a major oil field, cutting off President Bashar Assad's regime from key resources necessary for its long term survival. On Friday, activists also reported that rebels seized an air defense base and fought near two other army installations in Syria's north.