The top suspect in Monday's slaughter in Maguindanao has been formally charged with multiple murder before the Philippine Department of Justice, local media reported Thursday.

Justice Secretary Agnes Devanadera, together with Chief State Prosecutor Jovencito Zuno, performed the inquest at the General Santos City airport Thursday, according to Inquirer.net, the website of the Philippine Dauly Inquirer, the country's biggest broadsheet.

Andal Ampatuan Jr., mayor of Datu Unsay town in Maguindanao Thursday surrendered himself to the authorities after he and his family clan are tagged as prime suspects in Monday's massacre of at least 57 unarmed civilians.

Ampatuan is the son of Maguindanao Governor Andal Ampatuan Sr. and scion of a powerful family in central Mindanao.