A third mass grave was uncovered in the Philippines yesterday, bringing the number killed in the country’s worst political massacre to 57.

Police said that they had arrested several gunmen linked to a powerful politician over Monday’s massacre of political activists and journalists in the southern island of Mindanao.

Police did not say how many were arrested but said they were militiamen under the control of Andal Ampatuan Jnr, who is mayor of the town of Datu Unsay and the son of a key ally of President Arroyo. The father is also the most powerful clan leader in the province of Maguindanao. “Those who were abducted and murdered . . . were initially stopped by a group led by the mayor of Datu Unsay,” said Chief Superintendent Leonardo Espina.

The victims were relatives and supporters of an opposition politician, travelling to register his candidacy in next year’s election for the provincial governorship, as well as journalists covering the event.

Mr Ampatuan Sr is the key local supporter of Lakas Kampi CMD, the coalition Government led by Ms Arroyo.

Throughout her presidency, she has been accused of turning a blind eye to extrajudicial killings, which have often been blamed on the security forces. Ms Arroyo declared a state of emergency in Maguindanao and neighbouring areas on Tuesday, sending extra troops and police, and promising to find the killers.

“This is a supreme act of inhumanity that is a blight on our nation,” she said as she declared yesterday a national day of mourning. “The perpetrators will not escape justice. The law will hunt them until they are caught.”

But human rights groups were scathing after reports that Jesus Dureza, a senior official of the President, had met Mr Ampatuan Sr and other members of his family soon after the murders.

“They have assured us that they will co-operate fully in the investigation,” said Mr Dureza, the President’s adviser on the southern area.

Human Rights Watch expressed “deep concern that the administration’s personal relationships with the Ampatuan family were likely to hinder, rather than aid, an impartial investigation”.

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