A powerful improvised bomb exploded at dawn, startling people on their way to Good Friday religious ceremonies in the southern Philippines, police said.
No one was injured in the blast at Kalamansig although a store was slightly damaged, said Chief Inspector Celestino Daniel, the town police chief.
Military bomb experts said the device was similar to ones used by Muslim rebels.
"We are not sure who did it, we are still investigating," Daniel said.
Police and military in the town had already been on alert due to reports that Muslim extremists might launch attacks on the southern island of Mindanao during Holy Week celebrations.
The largely-Christian town had previously been attacked by Muslim separatists in August following the Supreme Court's rejection of a draft accord that would have given the rebels control over a large part of Mindanao.