The curfew in Colombo was lifted even as military surveillance aircraft kept an eye on the country’s main airports and naval units patrolled the waters around the island nation.

Over the weekend: The Islamic State said its fighters were among those killed in a raid on a house in eastern Sri Lanka that left 15 people dead and that wounded the wife and child of Zaharan Hashim, believed to be the mastermind of the bombings.

Go deeper: The town of Kattankudy is one of the few predominantly Muslim towns in Buddhist-majority Sri Lanka. It’s also Mr. Zaharan’s hometown and where he preached his divisive ideology.

Political fallout: Repeated failures in preventing and investigating the attacks have exposed rifts in Sri Lanka’s government, raising questions about the country’s ability to deter future threats.