A third bomb exploded in Mindanao Wednesday night on the eve of the 12th Association of Southeast Asian Nations (ASEAN) in Cebu, local television network ABS-CBN News reported.
The blast happened in a street in Cotabato City at 22:45 local time (14:45 GMT), injuring at least one person, said the report. The explosion was traced to an improved explosive device placed inside a trash can.
The blast in Cotabato City occurred two hours after a second bomb went off in Kidapawan City in Cotabato province, southern Philippines, seriously wounding a 14-year-old boy.
The first and deadliest bomb attack on Wednesday took place in General Santos City, killing at least six and wounding 26.
Authorities have placed the entire southern Mindanao region on Alert Level 4 or "critical" security level with the cities of Metro Manila and Cebu remaining on Alert Level 2 or "moderate."
The Philippine military went on red alert nationwide ahead of the ASEAN summit, which will officially begin Thursday with ministerial meetings in Cebu.
Canada, Britain and Australia have all renewed warnings against traveling to Cebu and Mindanao during the summit.
The Philippines abruptly postponed the ASEAN summit last month, apparently due to a typhoon threat, days after the United States, Britain, Australia and New Zealand issued travel warnings to the area.
(Xinhua News Agency January 11, 2007)