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 neighboring countries exchanged fire for several days after India's missile attack on Pakistan before reaching a ceasefire on Saturday.

The truce came after several days of the countries’ most expansive fighting in decades. One Indian official said the country would “deal strongly” with any violations.