Pakistan says it has shot down two Indian Air Force jets in a major escalation of the Kashmir conflict.
A spokesman said one plane had fallen inside Pakistani territory and two pilots had been captured. India has not yet given details.
Pakistan has denied reports one of its jets was shot down.
Both India and Pakistan claim all of Kashmir, but control only parts of it.
The nuclear powers have fought three wars since independence from Britain in 1947.
All but one were over Kashmir.
The aerial attacks across the Line of Control (LoC) dividing Indian and Pakistani territory are the first since a war in 1971.
They follow a militant attack in Kashmir which killed 40 Indian troops – the deadliest to take place during a three-decade insurgency against Indian rule in Kashmir.
A Pakistan-based group said it carried out the attack.