At least one suicide bomber in the Easter attacks in Sri Lanka trained with Islamic State in Syria, people with knowledge of the investigations said, reflecting the extremist group’s continued reach after the collapse of its self-declared caliphate.

The first direct links between Islamic State and those who carried out the deadly bombings came as the group released on Monday a rare recorded video purportedly of its leader, 47-year-old Abu Bakr al-Baghdadi.

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