One official said the group had to have had help from “an international network,” which he did not name.

The government acknowledged that a foreign intelligence agency gave Sri Lanka’s security officials a detailed warning of a possible attack on churches by the group at least 10 days ago. But bitter political infighting may have led to the catastrophic failure to pass the warnings on. Here’s the latest.

Blasts — possibly from police officers detonating suspicious packages — hit parts of the country on Monday, compounding an atmosphere of fear and grief that hangs over the country.

Closer look: We have maps of the sites of Sunday’s bombings, and photographs and video from Monday.

Victims: Identities of those who died are beginning to emerge. Among them were several dozen foreigners — three of them the children of a Danish billionaire.