More than 100,000 soldiers and police are being deployed across the Philippines to provide security ahead of elections due in May.
The BBC reports the aim is to enforce a ban on all unlicensed weapons and encourage private militias to disband.
Fifty-seven people were killed in the southern province of Maguindanao in November.
The incident was widely believed to have been related to the forthcoming elections in May.
The main suspect is a member of a politically powerful family that has long provided strong support for President Gloria Arroyo. He is accused of killing relatives of a rival political clan.
A number of journalists and lawyers were also killed. Their convoy was stopped at a check point before the killings were carried out.
Afterwards, the entire police force of the province was removed.
