MANILA, Philippines - The National Bureau of Investigation (NBI) has assigned 25 agents to secure Datu Unsay Mayor Andal Ampatuan Jr. at the Department of Justice (DOJ) for Friday's preliminary investigation into the multiple murder charges filed against him for allegedly leading the Maguindanao massacre.

Ric Diaz, head of the NBI's counter-terrorism unit, said Ampatuan Jr. will be transported from the NBI headquarters on board a bulletproof van.

Diaz added that Ampatuan Jr. will be handcuffed and made to wear a bulletproof vest.

The same kind of security will be provided by the NBI to Kenny Dalandag, the government's star witness in the gruesome mass killing of 57 innocent people in Ampatuan town, Maguindanao province last November 23.

The NBI said the Philippine National Police (PNP) will also provide security for the mayor and the witnesses during the preliminary hearing on Friday.

Several witnesses have placed Ampatuan Jr. at the site of the massacre in Barangay Saniag, Ampatuan town and told police that he directly participated in the massacre.

Ampatuan Jr.'s father, former provincial governor Andal Ampatuan Sr., and more than 190 people have also been charged by police for the massacre.

One of the witnesses, a local government official in Maguindanao, has implicated Ampatuan Sr. in his testimony. The witness said he overheard the former governor tell his son, Ampatuan Jr., to go on with the killing. (Read: New witness recounts merciless killings)

Among those killed were the wife of Maguindanao gubernatorial candidate Esmael "Toto" Mangudadatu, his two sisters, and 30 journalists.

Authorities believe the killing was election-related due to reports that Ampatuan Jr. was being groomed by his family to succeed the gubernatorial post.