Former Philippine President Gloria Arroyo pleaded not guilty to charges of electoral fraud, as her high-profile trial got underway in Manila on Thursday.

The 64-year-old Ms. Arroyo appeared at the brief arraignment hearing, smiling and wearing a white neck brace because of a spinal injury.

She is accused of conspiring with a notorious warlord to rig the 2007 senatorial elections in her party's favor.

Ms. Arroyo's lawyer Ferdinand Topacio told reporters outside the court that he is optimistic his client will be acquitted.

“Mrs. Arroyo personally stood and pleaded not guilty. We're very hopeful. This arraignment is the first step towards acquittal, so that this case will move forward.”

It is the first of several charges being brought against Ms. Arroyo by her successor, President Benigno Aquino.

Ms. Arroyo, president from 2001 to 2010, says the charges are politically motivated and designed to boost the popularity of Mr. Aquino.

Outside the courtroom, a small group of Arroyo supporters held signs and chanted slogans in support of her innocence.

“I don't think she (Arroyo) is guilty. We are not sure if the charges against her are true.”

Following her hearing, Ms. Arroyo was escorted amid heavy security back to a military hospital where she is being treated for what she says is a rare bone disease.