SRINAGAR, Kashmir — On Tuesday, the sound of explosions woke Srinagar up.

At 4:30 a.m., residents heard the dull thud of grenades and the rapid bam-bam-bam hammering of machine-gun fire.

Srinagar is the biggest city in the Indian-controlled zone of disputed Kashmir, and Kashmiris are sadly familiar with the sounds of war. But this was coming from an unusual place: the city’s heavily fortified international airport.

Three militants, who the Indian authorities said had slipped in from neighboring Pakistan, attacked a paramilitary camp near the airport, setting off a prolonged gun battle that lasted for hours and shut down the airport for the better part of the day.

It was the boldest strike in recent months, and though government troops eventually overpowered the militants and killed them all, the attack raised troubling questions about the airport’s level of security.