Pakistan called India's actions “irresponsible" and canceled visas for Indian nationals, suspended all trade with India and closed its airspace to Indian aircraft.

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

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, raising fears of military escalation between the nuclear-armed rivals.