BEIRUT — Rebels captured a military air base in northern Syria on Tuesday, their second major strategic victory in as many days, activists said.

The assault on the Jarrah airfield in Aleppo province comes a day after opposition fighters seized the nation's largest dam, an iconic industrial symbol of the four-decade rule of President Bashar Assad's family. The rebels have had their biggest success in Syria's civil war in the northeast, and the twin victories appeared to indicate they were solidifying their control of large swaths of the country's once heavily-contested north.

The director of the Britain-based Syrian Observatory for Human Rights, Rami Abdul-Rahman, said that after days of sporadic clashes around the Jarrah airfield, rebels launched a major assault on the base on Monday and had overrun the facility by Tuesday morning.