**Security forces in the Philippines have made a series of arrests following the murder of 57 people in an election-related massacre.**Troops and police swooped on towns on the southern island of Mindanao, run by the powerful Ampatuan family.
They are reported to have rounded-up and disarmed a 200-member paramilitary force there.
The massacre took place on Monday as a convoy of vehicles used by a rival politician was ambushed.
President Gloria Arroyo declared a national day of mourning and promised that the gunmen would not escape justice.
Restive province
Police on Thursday named militiamen under the control of politician Andal Ampatuan Jr - the mayor of a town in the restive province of Maguindanao - as suspects.
National police director general Jesus Verzosa told local media that Mr Ampatuan Jr was also a suspect.
“We don’t have an exact number (of those arrested), but our policemen in the area have arrested several,” he said.
Military spokesman Lt Col Romeo Brawner said he expected Mr Ampatuan Jr to be “turned over peacefully to the authorities”.
President Arroyo has already declared a state of emergency in Maguindanao and the neighbouring Sultan Kudarat province.
Although prominent members of the Ampatuan family are allies of President Arroyo, they have been expelled from her party since the killings.
Philippine politician Ismael Mangudadatu has claimed that gunmen loyal to the Ampatuans ambushed his supporters as they were travelling to register his name for forthcoming elections.
Among the dead were Mr Mangudadatu’s wife, his two sisters and several key supporters, as well as at least 13 journalists who were travelling with them to witness his registration as an election candidate.
Analysts say the Ampatuans have effectively been in charge of Maguindanao for decades.
Andal Ampatuan Snr has served in the Philippines Congress and won the governorship of Maguindanao unopposed for several terms.
His son was reportedly planning a similarly unopposed run to replace his father but then Mr Mangudadatu decided to run as well.