The Indian army has vowed "heavy retribution" for the killing of its three soldiers in the disputed region of Kashmir on Tuesday.

The attackers had mutilated the body of one soldier in the Machil sector, army spokesperson Col Rajesh Kalia said.

He did not specify if the soldiers were attacked by Pakistani soldiers or militants fighting against Indian rule.

Tensions over the long-running dispute have intensified after an Indian army base was attacked in September.

Both India and Pakistan accuse each other of violating the 2003 ceasefire agreement.

Both sides have reported civilians and a number of soldiers being killed or injured in recent weeks, during which time the Line of Control (LoC), the de facto border that divides disputed Kashmir between the two nations, has seen intense exchanges of fire.

Both nuclear-armed states claim the territory in its entirety but control only parts of it. Two of the three wars fought between the two sides since independence have been over Kashmir.

Following the latest attack, there was heavy firing and shelling by both sides of the LoC in Machil, reports said.

"Retribution will be heavy for this cowardly act," Col Kalia said.

An Indian army officer told the Press Trust of India news agency that a "counter-infiltration patrol party of Indian army was ambushed by terrorists ahead of the fencing along the Line of Control in the forest belt in Machil sector in Kupwara district" on Tuesday.

He did give any further details.

The territorial dispute between India and Pakistan over Muslim-majority Kashmir has been running for decades.

After the 18 September army base attack on the Indian-administered side, the Indian military said it had carried out "surgical strikes" against suspected militants along the LoC.

Pakistan called the strikes an "illusion" and denied Indian claims it was behind the militant attack.

A subsequent BBC investigation found that while India did not airdrop commandos to hit militant camps or conduct ground assaults deep into Pakistani-administered territory, troops did cross the LoC a significant distance to hit border posts and then pulled back.

Pakistan said two soldiers were killed in the strikes. Two more are reported to have died in cross-border firing since.