Seventeen Indian soldiers and four suspected rebel fighters have been killed in an attack on an army headquarters in Indian-administered Kashmir, according to a statement by the army’s northern command.

"Four terrorists killed in counterterrorist operation at Uri. 17 soldiers make the supreme sacrifice," the command said on Twitter on Sunday, referring to the Uri area, about 100km west of the troubled northern region's main city of Srinagar.

The fighters first attacked a frontline base close to the border known as the Line of Control before moving on to the headquarters, army spokesman Colonel SD Goswami said.

Most of the fatalities happened in a tent that caught fire, Lieutenant General Ranbir Singh, the Indian army's director general of military operations, told the briefing in New Delhi.

Reuters television footage showed helicopters flying in to evacuate the injured as an operation continued to secure the area. Smoke rose from the compound, set in mountainous terrain. The Defence Ministry earlier put the number of wounded at 35.

India accuses Pakistan

India has accused Pakistan of being behind one of the most deadly attacks in Kashmir in a quarter-century-old armed rebellion.

Lieutenant General Singh said that Sunday's attack bore the hallmarks of Pakistan-based armed group Jaish-e-Mohammed. Evidence gathered at the scene indicated the attackers were foreign and their equipment bore Pakistani markings, he told Reuters news agency.

"Our men are ready to give a befitting response," Singh said in response to a reporter's question. He did not elaborate.

Earlier, Indian Prime Minister Narendra Modi strongly condemned what he called the "cowardly terror attack".

"I assure the nation that those behind this despicable attack will not go unpunished," Modi said in a series of Twitter posts.

Smoke billows out from inside an Indian Army base which was attacked by suspected rebels in Uri [EPA]

In an even stronger response, Indian Home Minister Rajnath Singh tweeted: "Pakistan is a terrorist state and should be identified and isolated as such."

Singh chaired a crisis meeting in New Delhi and cancelled planned trips to Russia and the United States.

Pakistan rejected allegations that it was involved. "India immediately puts blame on Pakistan without doing any investigation. We reject this," foreign ministry spokesman Nafees Zakaria told Reuters.

Tens of thousands killed

Army Chief Dalbir Singh Suhag and Defence Minister Manohar Parrikar are to visit Kashmir after the attack, the Indian media said.

The Himalayan region has been in the grip of deadly unrest for more than two months, with protesting residents clashing almost daily with security forces, in the worst violence to hit the region since 2010.

At least 87 civilians have been killed and thousands injured in the protests against Indian rule, sparked by the killing of a popular rebel leader in a gun battle with soldiers on July 8.

READ MORE: Two centuries of oppression in Kashmir

Kashmir is divided into two parts, one administered by India and the other by Pakistan.

India claims Pakistan has been supporting a violent secessionist movement in Kashmir. Islamabad has consistently denied this charge. It calls Kashmiri rebels freedom fighters.

Tens of thousands of people, mostly civilians, have died in the fighting.

Inside Story: What will it take to restore peace in Kashmir?

Source: Agencies