Three dead in Philippines prison riot

"The violence started from verbal heckling with adjacent dormintories... until a gunshot was heard," he said.

"That lead to an exchange of gunshots and chaos erupted. Everyone was on self-defence mode."

Chaclag said seven detainees who started the violence were identified and taken to an isolation area while authorities decide on disciplinary action.

Prison guards seized improvised pistols and bladed weapons from the inmates, he added.

The New Bilibid Prison has 18,000 inmates. Closed circuit TV cameras are installed at the facility, but only in strategic areas. Prison guards do not monitor inmates 24 hours.