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 yesterday, 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.

Yesterday, activists also reported that rebels seized an air defense base and fought near two other army installations in Syria's north.

Rebels have been trying for months to capture Aleppo's international airport, which lies east of the city in a complex with a smaller military airfield and an army base charged with protecting the area.

The base, home to the Syrian army's 80th Brigade, fell to rebel forces on Wednesday, and fighting has continued over the airports since, with both sides shelling each other's positions.

The Britain-based Syrian Observatory for Human Rights said yesterday that some 150 people had been killed in the fighting over the past two days, roughly half of them rebels and half of them government troops.

If the rebels were to capture the two airports, it would be a symbolic blow to the regime and could shift the strategic balance in northern Syria. The regime has used the airports to ferry supplies to its forces bogged down in the stalemated fight for Aleppo, though recent clashes near the airport have halted air traffic.

Elsewhere, the Observatory reported yesterday that rebels has seized an air defense base in the village of Hasil, southeast of Aleppo, and were clashing with the army at the nearby Kuwiras air base and around the Wadi al-Deif army base in Idlib province.

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