Colombo went on a high alert on Thursday following a “warning” of a potential explosion. Official sources said armed police were checking vehicles and the authorities have urged residents to remain vigilant and calm.

The alert comes days after the Easter Sunday attacks that killed over 350 people in the island nation.

On Thursday morning, employees of several organisations and institutions, including the Central Bank, were asked not to leave their premises for close to an hour.

A blast was reported on Thursday morning at a vacant plot near the magistrate’s court in Pugoda town, 40 km away from Colombo, and no one was injured in the incident, police said, adding that they were investigating the explosion.

Police have nabbed at least 60 suspects in connection with the Sunday serial bombings and are on the lookout for more.