At least four Pakistani soldiers were killed today in shelling by Indian forces in the disputed Kashmir region, the Pakistani army said, in the latest clash between the nuclear-armed neighbours who have also been exchanging heated challenges.

A decades-old dispute over the mostly Muslim Himalayan region of Kashmir, claimed in full but ruled in part by both Pakistan and India, has heated up in recent years after a 2003 ceasefire brought more than a decade of relative peace.

"Troops were busy in line communication maintenance when they were fired upon and hit by heavy mortar round," the Pakistani military said of the attack in which the four men were killed, in the Jandrot region.

Pakistani forces responded, killing three Indian soldiers and wounding several, it said.

India's military told Reuters that Pakistani forces fired first and no casualties were recorded on the Indian side.

On another section of the so-called Line of Control (LoC) dividing Kashmir between the two sides, India said its forces on Monday killed five member of a pro-Pakistan militant group trying to slip into Indian Kashmir.

"They crossed the Jhelum river which is de facto border in the area. We allowed them to cross the river and challenged them. All of the five who crossed the river were killed," said an Indian officer, Major General Gulab Singh Rawat.

A Pakistani military source, who declined to be identified, denied that any militants had been killed trying to cross from the Pakistani side to the Indian side.

India accuses Pakistan of backing Islamist militants and encouraging them to launch attacks in Indian-controlled Kashmir, where a separatist insurgency has simmered for years, and in other parts of India.

Pakistan denies that and says India must hold negotiations on the future of Kashmir.

The neighbours have fought three wars since their independence from Britain, two of them over Kashmir.

CALLING NUCLEAR BLUFF

Artillery exchanges across the LoC were common for years before the 2003 ceasefire in Kashmir largely brought an end to violence but clashes have again been increasing over the past couple of years.

Relations have been particularly tense since India said it had carried out cross-border surgical strikes against militants hiding in Pakistan in 2016.

Pakistan said Indian forces never crossed onto its territory.

On Friday, Indian army chief General Bipin Rawat said his forces were willing to carry out operations inside Pakistan despite the risk of a nuclear conflict, the Indian daily the Hindustan Times reported.

"If we will have to really confront the Pakistanis, and a task is given to us, we are not going to say we cannot cross the border because they have nuclear weapons. We will have to call their nuclear bluff," Rawat said at a press briefing.

The comment drew derision from Pakistan's foreign minister who termed the statement "irresponsible" and an "invitation for nuclear encounter".

"If that is what they desire, they are welcome to test our resolve. The general's doubt would swiftly be removed," Khwaja Asif said on Twitter.

Pakistan's military has said 52 civilians were killed and 254 wounded by Indian shelling in the region last year, more than in all of the previous 14 years combined.

The two sides accuse each other of repeated violations of the 2003 ceasefire.