Philippine police have identified at least two suspects in the bombing of a Catholic Mass that killed four people, a regional police chief said Monday, vowing to hunt down those behind the blast, which was claimed by Islamic State militants.

The bomb went off on Sunday during a service at a university gymnasium in Marawi, a city left in ruins in 2017 by a five-month military campaign to end a bloody occupation by Islamic State group loyalists that had triggered alarm across Asia.

"(We have persons) of interest, but the investigation is still ongoing. In order not to pre-empt the investigation, we will not divulge the names," regional police Chief Allan Nobleza told GMA News, adding that one of the suspects was linked to a local militant group.