In the surgical strikes spread over a 250 km arc, troops went 2 km deep into territory occupied by Pakistan, in terrain that included hills, forests and mountains, sources said.

Seven terrorist launch pads were targeted before the Indian troops returned around 4.30 am. Each terrorist launch pad had 30 to 40 terrorists and the army says there were "massive casualties".

A combination of ground forces and paracommandos were involved in what India called a preemptive strike.

"Full surprise was achieved," said sources. The troops started moving in the afternoon.

Heavy firing in Kashmir's Uri - the site of the terror attack in which 18 soldiers were killed earlier this month - was used as a distraction as soldiers were pushed into Pakistan Occupied Kashmir, sources say.

The soldiers had clear orders "not to leave bodies or buddies behind", said sources.

"Our forces have gone deep in and come back before sunrise," government sources said. Pakistan was caught off guard and opened fire this morning, India retaliated.

Sources say India has video evidence of the strikes, including some obtained through drones, which will be released when it is considered appropriate.

According to the army, the terrorists were planning attacks in Jammu and Kashmir and in metros. The launch pads had been under surveillance for about a week.