A group of between seven and 10 militants attacked a guard post and tried to force their way into the Badaber air base, Major General Asim Bajwa said on Twitter.
A gunbattle was still underway and three attackers had been killed so far, he said.
There was no immediate claim of responsibility for the attack from any militant groups.
Television pictures showed helicopters hovering above the base while police and ambulances gathered outside.
The number of attacks in Pakistan has fallen dramatically this year, due to a combination of a military offensive against Taliban bases along the Afghan border and government initiatives to tackle militancy.
That followed a massacre at a military-run school last December that killed around 150 people, almost all of them children.