Former Maguindanao Governor Andal Ampatuan Sr (centre) is surrounded by police at a court in Manila in March. A man who testified in court on the Philippines' worst political massacre -- for which Ampatuan is on trial -- was found dead "probably chain-sawed to pieces" in a killing meant to silence other witnesses, an official said Friday

A man who testified in court on the Philippines' worst political massacre was found dead "probably chain-sawed to pieces" in a killing meant to silence other witnesses, an official said Friday.

Esmail Amil Enog went missing in March after he spoke in court last year about the alleged role of a powerful political clan in the November 2009 murders of 57 people, prosecutor Nena Santos told AFP.

"The body was put in a sack and it had been chopped up, probably chain-sawed to pieces," Santos said, declining to give further details about when and where the body was found as it might endanger lives.

"If we mention someone he might also end up dead."

Marcelo Pintac, police chief of Maguindanao province where the massacre took place, told AFP Enog was officially reported as missing, but that he was unaware his body had been found.

Enog, an employee of the Ampatuan family of Maguindanao, had told the court that he had driven the clan's armed followers to a site where 57 victims were later abducted.

The victims, including relatives and lawyers of the Ampatuans' local political rival Esmael Mangudadatu as well as 32 journalists and media workers, were later found murdered in a mass grave.

Prosecutors allege the killings were intended to prevent Mangudadatu from challenging an Ampatuan clan member in elections for governor.

The massacre shocked the world and forced then-president Gloria Arroyo to crack down on her former allies, the Ampatuans who had ruled the southern province for decades.

Clan patriarch Andal Ampatuan Snr and several of his sons are among 64 people on trial in Manila for the massacre.

However, about 100 other suspects are still at large, many of them armed followers of the Ampatuans who still retain influence in the area.

Santos said Enog could have identified other suspects in the massacre, adding his death would frighten other potential witnesses.

Human Rights Watch researcher Carlos Conde said Santos's account of the killing fit into the pattern of potential witnesses in the case being intimidated or bribed.

"The murder was intended to send a message, to cause a chilling effect to other witnesses," he told AFP.

Conde said Enog had refused a government offer of protection, which was an indication something was wrong with the state's witness protection programme.

Another witness had already been murdered in 2010 and relatives of other witnesses had also been attacked, he added.