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.

In a dramatic turn of events, US President Donald Trump took to social media on Saturday to announce that India and Pakistan - after four tense days of cross-border clashes - had agreed to a "full and immediate ceasefire".

The ceasefire had been expected to bring a swift end to weeks of escalating clashes triggered by the mass shooting of tourists last month that India blames on Pakistan.