Ten prisoners in the Philippines were killed when a suspected jailbreak and attempt to kidnap the warden went wrong in a Manila suburb, authorities said today.

Philippine President Rodrigo Duterte is waging a drug war, resulting in the killing of hundreds of suspected drug dealers and the arrest of thousands more, packing overcrowded jails

The prisoners, including two Chinese, were meeting with the warden of the Paranaque City jail in his office when the explosion occurred on Thursday evening, killing the inmates and wounding the warden, said national jail service spokesman Senior Inspector Xavier Solda.

The blast comes as Philippine President Rodrigo Duterte wages a drug war, resulting in the killing of hundreds of suspected drug dealers and the arrest of thousands more, packing overcrowded jails.

Preliminary investigations showed the explosion was caused by a grenade, with a pistol also recovered from the scene, Solda told reporters.

"The initial investigation is that it was a possible jailbreak and hostage-taking," he added.

Solda described the dead men as high profile inmates, adding that eight of them, including the two Chinese, were linked to illegal drugs while the two others were jailed for robbery.

He said the inmates had asked to meet the warden but it was unclear why he did so without personal guards.

"The only one who can clear this up is the warden but he is in the hospital and may need an operation," Solda said.