India and Pakistan agreed to an immediate ceasefire on Saturday, unexpectedly halting the worst fighting in decades between the nuclear-armed neighbors, just when their tit-for-tat strikes appeared to be spiraling out of control.

The Indian military sent a “hotline message” to Pakistan on Sunday about violations of a ceasefire agreed this week and informed it of New Delhi’s intent to respond if it was repeated, a top Indian army officer said, while the Pakistan military’s spokesman denied any violation of the ceasefire.

The first word of the truce came from President Trump, who announced that the two countries had reached a "full and immediate ceasefire," after talks mediated by the U.S.