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.

At least 20 people were feared dead after suspected militants opened fire on them in India's Himalayan territory of Jammu and Kashmir on Tuesday, with officials saying it was one of the deadliest such attacks in recent times.

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