"Indian Air Force violated Line of Control," Pakistan military spokesman Major General Asif Ghafoor tweeted, referring to the de facto border between Indian- and Pakistani-administered Kashmir.

Pakistan Air Force jets were scrambled in response to the incursion, Ghafoor said.

"Facing timely and effective response from Pakistan Air Force (the Indian aircraft) released payload in haste while escaping near Balakot. No casualties or damage."

He did not provide further information on the location, and whether it was a town of that name in Pakistani-administered Kashmir or further into its territory.

Ghafoor tweeted images of what he said was the payload, showing what appeared to be pieces of metal in a heavily forested area.

There was no immediate comment from New Delhi.

However, Indian news reports said that air force jets hit multiple targets including camps run by Jaish-e-Mohammad, the Islamist group that claimed the February 14 suicide attack in Kashmir that sent tensions soaring.

"Top government sources said that there were nearly 200 casualties from the (Indian Air Force) strike," private broadcaster CNN News 18 said.

New Delhi had threatened to retaliate after the deadliest attack in three decades in Kashmir killed more than 40 Indian paramilitaries.

Islamabad has said it had nothing to do with the attack, and warned it will retaliate if India launches any strike.

JeM is one of several anti-Indian groups fighting in Kashmir, which has been claimed by both India and Pakistan since independence in 1947.

They have fought two of their three wars over the Himalayan territory.

Pakistan's interior ministry announced last week that authorities had seized control of a complex believed to be the JeM headquarters.