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.

The Pakistani government said that if India followed through on a threat to block rivers it would take it as “an act of war.”

Members of Jammu and Kashmir Awami National Conference shout slogans during a protest after a deadly attack that killed 26 people, mostly tourists, in Srinagar, Indian controlled Kashmir, Thursday, April.