MANILA - The Philippines' Supreme Court has junked plunder charges against former president Gloria Macapagal Arroyo, setting her free after nearly five years of detention.

Voting 11-4, the court ruled on Tuesday (July 19) that the evidence against the 69-year-old Mrs Arroyo was "insufficient", and ordered her "immediate release".

She was accused of stealing 399 million pesos (S$12.2 million) from the state lottery firm when she was president from 2004 to 2010.

Mrs Arroyo, who is serving a third term as a lawmaker, was first arrested in November 2011, after she was accused of rigging the 2007 elections.

She was held at the Veterans Memorial Medical Centre, as she had been suffering from debilitating neck arthritis.

She was allowed to post bail in July 2012, but was again arrested and held under hospital arrest in October 2012 on a plunder case filed by an anti-graft court under then President Benigno Aquino, 56.

That case was dismissed on Tuesday (July 19).

"It has been a long, long Good Friday for Mrs Arroyo, but it is now over. As of this minute, she can consider herself free and in liberty," said Mr Estelito Mendoza, one of Mrs Arroyo's counsel.

In a statement, Mrs Arroyo's husband Mike Arroyo said the Supreme Court's ruling "has validated what we have been saying for six years now: that the charges against former president Gloria Macapagal-Arroyo are nothing more than disingenuous attempts at political persecution by a corrupt and inept Aquino administration intent on covering up its gross lack of accomplishments by harassing its political opponents".

President Rodrigo Duterte, 71, earlier offered to pardon Mrs Arroyo, as a former president.

But Mrs Arroyo declined, insisting that a pardon meant admitting guilt.

Mrs Arroyo has been among the first politicians to back Mr Duterte's bid to become president.

A United Nations working group on arbitrary detention earlier found Mrs Arroyo's continued detention "arbitrary" and "violates international law".

The UN report said criminal cases filed against Mrs Arroyo have been "politically motivated since she is detained as a result of the exercise of her right to take part in government and the conduct of public affairs" and for her "political opinion".

Mrs Arroyo's case was taken up by Mrs Amal Clooney, a human rights lawyer and wife of Hollywood actor George Clooney.