The device exploded shortly before midnight at the office of Carmona Mayor Roy Loyola, severing the left hand of the suspected bomber, Domingo Alwardo, said Chief Superintendent Enrique Galang, Calabarzon police director.
Carmona town is about 40 kilometers south of Manila.
Alwardo, a supporter of Carmona Vice Mayor Ador Alumia, also sustained third-degree burns on his face and body. Responding policemen and barangay tanods caught him while scaling the five-foot high concrete perimeter fence of the town hall shortly after the blast at 11:30 p.m.
Galang said the suspected bomber was trying to plant the device in the ceiling when it exploded prematurely.
"When he was interrogated, he admitted that if given the opportunity, he would really kill the mayor," Galang said, adding the man mentioned a grudge over a land problem.
An unexploded hand grenade and a cellphone, which could have been intended as a timing device, were recovered from the site.
Loyola, in a radio interview with Manila radio station dzBB, blamed Alumia, pointing out that Alwardo was the vice mayor’s supporter.
Alumia admitted in the same program that Alwardo was his supporter but denied ordering the bombing.
Police said Alwardo has alleged that Alumia and his brother Dennis masterminded the bombing.
Superintendent Mariano Manaog, Carmona police chief, said probers have questioned Dennis whom witnesses saw in Alwardo’s company in the vice mayor’s office at about 4 p.m. Thursday.
Manaog suspected that Alwardo allegedly stayed in Alumia’s office until dark and then crawled in the ceiling to reach Loyola’s office at the right wing of the newly built municipal building.
Loyola said it was the third attempt to kill him this year.
Loyola and Alumia have been locked in a court battle since last year over graft charges. Alumia accused Loyola of committing graft over the payment of phone bills of school officials. The Ombudsman subsequently cleared Loyola of the charges.
Gov. Ayong Maliksi suspended Alumia for 60 days last year in connection with graft complaints filed by two barangay chairmen against him.