Relations between India and Pakistan are cratering following a deadly attack in the disputed Himalayan region of Jammu and Kashmir that left more than two dozen tourists dead.

All but one of the 26 people massacred in the attack on Tuesday were Indian citizens, prompting a new wave of unrest in a region at the epicenter of long-running and often violent territorial struggle between Pakistan and India.

On Wednesday, India accused Pakistan of supporting terrorist groups in the region, after a little-known militant group called The Resistance Front claimed responsibility for the attack. Pakistan has denied any involvement.

New Delhi has since downgraded ties with Islamabad, shut a key border crossing, and suspended for the first time its involvement in a crucial water-sharing treaty, among other punitive measures, triggering Pakistan to announce a host of retaliatory measures including the suspension of trade. Both sides have cancelled visas of each others’ nationals.