Police and radio reports said at least 11 people, including a four-year-old child, were also injured by the bomb discovered in a box inside the bus terminal of Pagadian, the capital of Zamboanga del Sur.
Killed on the spot were SPO4 Humberto Remoto, SPO4 Beljoe Curator and Ryan Akyatan, according to Superintendent Ajijul Taradji, Zamboanga del Sur police chief.
Taradji identified the wounded policemen as Chief Inspector Dionecio Perdiguez, Pagadian City police commander; his deputy Senior Inspector Junie Sagun; SPO4 Lily Palmero, PO3 Bienvenido Legazpi, and PO1 Arthur Balatan.
The wounded civilians were Romeo Estara, Michael Denver, Acub Mohammad, Teodolo Solas, Leo Anasco, Jerosin Rasete, Moteami Tambos, Guillar Tambos, and Abusama Ibrahim.
Most of the victims were passengers waiting in the bus station. Those wounded were rushed to Pagadian City Medical Center for treatment.
A reporter for Radio Mindanao Network who witnessed the explosion said a civilian security guard moved the bomb with a clock as a timer outside of the bus terminal and placed old tires around it before calling the police.
Last month, police discovered a bomb in the same bus terminal and successfully defused it.
This time, the bomb exploded as police tried to move it to a safe area for detonation, a police report said.
The bystanders were hit with shrapnel and severe burns to several parts of their body, according to witnesses.
The police did not immediately name any suspects in the attack. "It is not yet clear to us as to who is the perpetrator and who masterminded this bombing," Taradji said in a phone interview.
Authorities have blamed past attacks in Pagadian on the Moro Islamic Liberation Front, a Muslim separatist group that is currently holding peace talks with the government.
Those wounded were identified as Rolly Tagatac, security guard Rene Bontigao, Carlito Nodalo, Rogelio Caberte, Reynaldo Bongcab, and Marilyn Bongabong.
Marine Col. Frank Gudani, deputy chief for operation of the Armed Forces Southern Command, said that prior to the explosion, the victims were having a drinking spree inside the warehouse. Tagatac allegedly played with the grenade and accidentally pulled out its safety pin. With Jaime Laude