MANILA >> One of three Philippine senators accused of plunder refused to enter a plea Thursday during arraignment by the anti-graft court in the biggest corruption trial in the country in more than a decade.

The court instead entered a not guilty plea for Sen. Ramon Revilla Jr., an action movie star accused of receiving $5.1 million in kickbacks from a scam that allegedly diverted millions of dollars from anti-poverty and development funds allotted to lawmakers’ pet projects.

The high-profile prosecutions bolster President Benigno Aquino III’s campaign to fight high-profile corruption that has plagued the nation of 97 million for decades. The problem has festered amid a culture of impunity among powerful politicians and their allies, weak law enforcement and a notoriously slow justice system. Still, it’s unclear whether the charges will lead to convictions, which have been rare in major cases.

Revilla has denied taking kickbacks or stealing money from state funds, but his lawyer Joel Bodegon said he advised the senator not to enter a plea so that several pending motions questioning the validity of the charges will not be dismissed.

Two other prominent senators are accused in the case — Juan Ponce Enrile and Jinggoy Estrada. They have not been arraigned yet.

Estrada, son of an ex-president and now Manila Mayor Joseph Estrada, joined Revilla in detention at the national police headquarters on Monday. He is accused of pocketing $4.2 million in kickbacks.

Enrile allegedly pocketed $3.94 million in kickbacks, but an arrest warrant has not been issued yet for the 90-year-old former senate president.

Estrada and his father were also accused of plunder in 2001 in a landmark trial that followed the president’s ouster in a popular uprising. The younger Estrada was acquitted in 2007, but his father was convicted of illegally amassing about $81 million in bribes and proceeds from illegal gambling. He was later pardoned by his successor.

Bodegon said that his client, Revilla, feels the cases are politically motivated to hurt his chances for running for president in 2016. A bail hearing will be held next month for Revilla.

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Associated Press writers Jim Gomez and Teresa Cerojano contributed to this report.