Philippine President Gloria Macapagal-Arroyo on Tuesday placed three provinces in southern Mindanao region under the state of emergency following Monday's bloody political massacre that left at least 24 people killed.

The Presidential Office said the move is to "prevent and suppress lawless violence" in provinces of Maguindanao, Sultan Kudarat, and Cotabato city. The order started to be in effect on Tuesday and remains so until being lifted by the president.

Around 100 militiamen believed to have close ties with Maguindanao Governor Andal Ampatuan Monday ambushed a convoy of at least 40 supporters of Buluan town vice mayor Ismael Mangudadatu on their way to register him as the candidate for the governor's post against Ampatuan's son.

Militiamen fired M-16 rifles and killed at least 24 people, most of whom are women, police officials said Tuesday. National police chief Jesus Verzosa on Tuesday flew to the south to oversee the rescue and recovery operations.

Presidential Adviser for Mindanao Jesus Dureza described the assassination as a "gruesome massacre unequaled in recent history " in a statement obtained by Xinhua.

Dureza recommended the state of emergency to ensure "everyone be disarmed".

Maguindanao is part of the Autonomous Region of Muslim Mindanao, a Muslim-dominating area created by a peace pact signed between the government and a large Muslim rebel group in 1996. Clan wars were frequent and fatal in Mindanao, the insurgency-infested region flooded with loose weapons.

Amputuan family reportedly owns a private army composed of 100 fully armed militiamen.