Pakistan is ready to help India investigate the deadliest blast in Kashmir in decades but will retaliate if Delhi attacks, Prime Minister Imran Khan said Tuesday as tensions between the nuclear-armed rivals soared.

Khan used a nationally televised address to demand Delhi share proof of Islamabad’s involvement in last week’s suicide blast, which killed 41 people in Indian-held Kashmir and unleashed a fresh diplomatic crisis over the disputed Himalayan region.

The attack was claimed by Pakistan-based militant group Jaish-e-Mohammed. Indian officials have said those behind the blast will pay a “heavy price”.

If India attacks, “Pakistan won’t just think to retaliate. Pakistan will retaliate,” says Khan in the address.

Pakistan has denied involvement. Khan said on Tuesday that if any militant group was using Pakistani soil to launch attacks, “its enmity is with us. This is against our interest”.

“If you have some actionable intelligence about involvement of Pakistanis, give it to us, I guarantee you that we will take action,” he adds.

Kashmir has been split between India and Pakistan since independence from Britain in 1947. Both countries claim the Himalayan territory in full and have fought two wars in connection to the dispute.

India has long accused Pakistan of harbouring militants that launch attacks on its soil, while Islamabad has repeatedly vowed to crack down on the groups if Delhi provides evidence of involvement.

Moments after the address, Khan’s official Instagram account posted a picture of the premier scowling and cross-armed along with a message that read: “Don’t mess with my country”.

Less than an hour after it was posted, the message had more than 23 000 likes.

Khan’s speech comes as India said it had killed the alleged militant behind the attack.

Earlier this week, Saudi Arabia vowed to “de-escalate” the situation during a high-profile state visit by Crown Prince Mohammed bin Salman to Islamabad. He is also due in India this week.

Kashmir is one of the world’s most militarised zones, with some 500 000 Indian troops deployed to fight a rebellion that broke out in 1989.

Scores of armed groups are now involved.

Tens of thousands of people, mainly civilians have died in the conflict. Violence has spiked since 2016 with almost 600 killed last year, the highest toll in a decade.