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.

A day after the U.N. appealed for restraint following Tuesday's deadly attack in Indian-administered Kashmir, India reported an exchange of fire across the de facto border in the disputed region.

The risk of exposing a military still being modernized may constrain Prime Minister Narendra Modi as he weighs retaliation for a terrorist attack.