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.

New developments in the nuclear powers’ harrowing four-day conflict, along with entrenched religious nationalism on each side, could signal more frequent battles ahead.

But hours after the deal was confirmed, there have been accusations that the agreement is not being entirely upheld.