New Delhi regularly blames Islamabad for backing gunmen in Kashmir, who have fought an insurgency against Indian forces since 1989.

Islamabad denies it backs the insurgents, saying it only supports Muslim-majority Kashmir's struggle for self-determination.

The killing of 26 people in Indian-run Kashmir on Tuesday signalled a dramatic escalation in violence -- targeting civilians and the area's vital tourism industry -- and a shift from the common small-scale clashes between militants and security forces.

India on Wednesday took a raft of diplomatic measures against Islamabad, including shutting its key land border crossing and suspending a water-sharing treaty.

Pakistan then announced a meeting of its National Security Committee, summoned only in cases of external threat or major attack.

Here are key events in their troubled relationship.

- 1947: Partition and war -

Two centuries of British rule end on August 15, 1947, with the sub-continent divided into mainly Hindu India and Muslim-majority Pakistan.

The poorly prepared partition unleashes bloodshed that kills possibly more than a million people and displaces 15 million others.

Kashmir's monarch dithers on whether to submit to Indian or Pakistani rule.

But, after the suppression of uprising against his rule, Pakistan-backed militants attack. He seeks India's help -- precipitating an all-out war between both countries.

A UN-backed, 770-kilometre (478-mile) ceasefire line in January 1949 divides Kashmir, known as the Line of Control.

- 1965-71: Kashmir and Bangladesh wars -

Pakistan launches a second war in August 1965 when it invades Kashmir.

The conflict ends seven weeks later after a ceasefire brokered by the Soviet Union with thousands of soldiers dead on each side.

Pakistan deploys troops at the start of 1971 to suppress a growing independence movement in what is now Bangladesh, which it had governed since 1947.

An estimated three million people are killed in the nine-month conflict and millions more flee into India.

India invades Bangladesh, forcing Pakistan's surrender in 1971.

- 1989-90: Rebellion in Kashmir -

An uprising breaks out in Kashmir in 1989 as longstanding grievances at Indian rule boil over.

Hindus and other minorities flee the region over the following year after targeted assassinations, assaults, and threats by rebel fighters.

Tens of thousands of soldiers, rebels and civilians are killed in the following decades in clashes between security forces and militants.

India accuses Pakistan of funding the rebels and aiding their weapons training.

- 1998-99: Nuclear weapons and Kargil conflict -

Pakistan conducts its first public nuclear weapons tests in 1998, following India, which first conducted tests in 1974.

Pakistan-backed militants cross into Indian-administered Kashmir in 1999, seizing military posts in the icy heights of the Kargil mountains.

Raja Mohammad Zafarul Haq, a leading member of Pakistan's ruling party, says his country will not refrain from using nuclear weapons to protect its security if necessary.

Pakistan yields after severe pressure from Washington, alarmed by intelligence reports showing Islamabad had deployed part of its nuclear arsenal nearer to the conflict.

Pakistan's then prime minister Nawaz Sharif blames army chief Pervez Musharraf for igniting the conflict, which killed at least 1,000 people over 10 weeks, without his knowledge or approval. Musharraf overthrows Sharif in a coup months later.

- 2008-Present: Mumbai attacks and Modi -

Islamist gunmen attack the Indian financial hub of Mumbai in 2008, killing 166 people.

India blames Pakistan's intelligence service for the assault and suspends peace talks. Contacts resume in 2011, but the situation is marred by sporadic fighting.

Indian Prime Minister Narendra Modi makes a surprise visit to Pakistan in 2015 but the diplomatic thaw is short-lived.

A 2019 suicide attack kills 41 Indian paramilitary troops in Kashmir and prompts Modi to order airstrikes inside Pakistan.

The resulting stand-off between the two nations is swiftly defused and Modi is re-elected months later, partly on a wave of nationalist fervour spurred by the military response.

Later, Modi's government cancels Kashmir's partial autonomy, a sudden decision accompanied by mass arrests and a months-long communications blackout.

In 2021, both nations reaffirm a 2003 ceasefire, but Pakistan insists that peace talks can resume only if India reinstates Kashmir's pre-2019 autonomous status.