MANILA, Philippines - A powerful Muslim clan carefully planned and carried out the killings of 57 people -- including 30 journalists -- in the Philippines' worst massacre, a witness said Wednesday as the landmark trial began.

Lakmudin Saliao's testimony directly linked Andal Ampatuan Jnr, the main defendant, to the planning and execution of the killings in the clan's former fiefdom of Maguindanao, an impoverished province in the troubled south.

The former mayor is accused of carrying out the November 23, 2009 killings of relatives of a rival politician who had challenged him for the post of governor and the 30 journalists, and two drivers, travelling in a convoy.

Saliao, 33, a former trusted aide of the Ampatuan family, said he attended a clan leaders' meeting at the home of the main defendant's father and namesake, Andal Ampatuan Snr, six days before the massacre to plan how to stop the rival.

"That's easy, father. We kill all of them when they come here," Saliao quoted Ampatuan Jnr as telling his father.

Ampatuan Jnr, in his 40s and heir-apparent to one of the most powerful Muslim political clans in the south, faces life in prison if convicted.

Ampatuan Snr, one of six Ampatuan defendants in the case, had ruled Maguindanao for nearly a decade and wanted to pass on the governor's post to his son.

Saliao said Ampatuan Snr then explained to his son how the killings should be carried out.

"Do not entrust the roadblock to others. You yourself should stop them at the highway, near the place where a backhoe is conducting some diggings," the witness quoted the patriarch as saying.

"Many of those in the room laughed and said they all agreed to have them killed," said Saliao, who told the court he was beside Ampatuan Snr during the meeting and clearly heard the statements.

In all 196 people are facing charges related to the massacre, although more than 100 of the alleged gunmen remain at large.

Saliao said he stayed at the Ampatuan home on the day of the massacre, helping the father give orders to son over a mobile telephone.

He said he later heard the son tell his father over speaker phone how the son had stopped the rival's convoy and subsequently carried out the killings. The patriarch then told his son to leave the scene of the crime, Saliao said.

Saliao said the father had wanted to spare the journalists in the convoy, but Ampatuan Jnr insisted on killing them all to leave no witnesses alive.

"Let us kill all of them. Some may talk if we spared them," Ampatuan Jnr told his father, according to Saliao.

"After a few minutes, Unsay (Ampatuan Jnr) called and said 'Father, it is done. They are all dead,'" he said.

"Very happy," Saliao said when asked about the elder Ampatuan's reaction.

Ampatuan Jnr, wearing a yellow prison shirt and flanked by jail guards, sat impassively behind his lawyers as the witness took the stand. He refused to talk to reporters after the hearing.

Nena Santos, a lawyer for some of the victims' relatives, cautiously welcomed the start of the trial, but added the Ampatuans remained powerful and could intimidate witnesses even from behind bars.

"We started today with a smoking gun as you can see," Santos said, noting that Saliao's credibility was unassailable because he practically grew up in the Ampatuan household.

Saliao, she said, also knew about alleged intimidation of witnesses as well as supposed attempts to bribe them.

Editha Tiamzon, widow of one of the murdered journalists, sat teary-eyed as Saliao recounted the killings.

"It is painful to hear my husband's painful ordeal," she said. "I am satisfied the trial has begun after many delays, but there is a long way to go."

Journalist's husband Noemi Parcon, who was also widowed in the attack, said she believed the testimony gave them hope that justice will be served.

"It will have a big influence on the case," she said.

Saliao was expected to continue his testimony when the resumes next week.