At least 26 people were killed and 17 others wounded when gunmen opened fire on tourists in Indian-controlled Kashmir, the worst assault in years targeting civilians in a restive region that has seen an anti-India rebellion for more than three decades.

India's Prime Minister Narendra Modi says the gunmen behind a terrorist attack on tourists in the Kashmir region "will not be spared!"

The Pakistani government said it did not want an escalation, but in the wake of a deadly attack in Indian-controlled Kashmir by unidentified militants, analysts warned of an unpredictable situation.