NEW DELHI — A deadly attack on tourists in Indian-controlled Kashmir has again moved India and Pakistan closer to war as the two rivals downgraded diplomatic and trade ties, closed the main border crossing and revoked visas for each other’s nationals.

Relations between India and Pakistan are cratering following a deadly militant attack in Indian-administered Kashmir that has sparked tit-for-tat reprisals and raised fears of another military escalation between the nuclear-armed rivals.

At least 26 people were killed and 17 others wounded when gunmen opened fire on tourists in Indian-controlled Kashmir, the worst assault in years targeting civilians in a restive region that has seen an anti-India rebellion for more than three decades.