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.

Twenty-six men were killed and 17 were injured when suspected militants opened fire at tourists in India's Jammu and Kashmir territory, police said.

India has summoned the top Pakistani diplomat in New Delhi, local media reported on Thursday, a day after it announced measures to downgrade ties with Islamabad as relations between the nuclear-armed rivals plummeted following a deadly militant attack in Kashmir.