France, May 8 -- Indian and Pakistani soldiers exchanged gunfire overnight in Kashmir, New Delhi said Thursday, a day after the worst violence between the nuclear-armed rivals in two decades.

Pakistani Prime Minister Shehbaz Sharif vowed to retaliate after India launched deadly missile strikes on Wednesday morning, with days of repeated gunfire along their border escalating into artillery shelling.

"We will avenge each drop of the blood of these martyrs," Sharif said, in an address to the nation.

India said it had destroyed nine "terrorist camps" in Pakistan in "focused, measured and non-escalatory" strikes, two weeks after New Delhi blamed Islamabad for backing an attack on tourists in the Indian-administered side of disputed Kashmir-...