But Zaldy Ampatuan, former governor of Autonomous Region in Muslim Mindanao, and his uncle, Akmad Ampatuan, former mayor of Mamasapano town on the southern island of Mindanao, will remain in detention until a local court orders their release.

"Mere relationship, having the same name does not establish conspiracy," Alberto Agra, acting secretary of the Department of Justice told reporters, saying the evidence against Zaldy and Akmad Ampatuan are weak.

"I ordered the prosecutors to remove the names of Zaldy and Akmad Ampatuan from the list of accused," Agra said after state prosecutors reviewed the evidence against them.

The justice department's resolution to drop murder charges against the two members of Ampatuan clan immediately drew sharp criticism from opponents of President Gloria Macapagal Arroyo, saying she was trying to protect her political allies.

"This is evidence that the victims cannot get justice under the administration of President Arroyo," Harry Roque, a lawyer for some of the massacre victims, told reporters.

On Friday, security forces transferred Andal Ampatuan Sr, the patriarch of the powerful clan, his three sons and a brother from police and army bases in the south to a detention facility in the capital.

Agra said Zaldy's lawyers had submitted certificates from a local mobile phone company and a local airline to show he was in Manila when the massacre happened. Some witnesses also gave affidavits to corroborate Zaldy's defense.

Agra said there were no witnesses against Akmad, a brother of the Ampatuan patriarch. Police investigators did not name him among the suspects in their reports, he added.

Last November, seven members of a rival clan, 20 civilians and 30 journalists were killed by about 100 armed men in southern Maguindanao province.

Those killed had been on their way to witness the filing of nomination papers of a candidate preparing to stand against the key suspect, Andal Ampatuan Jr, for a local position in next month's elections.

The deaths heightened the Philippines' profile as one of the most dangerous places in the world for journalists and stoked tensions ahead of national and local polls on May 10.