Image caption Gloria Arroyo pleads not guilty and ''feels the case is an injustice''

Former Philippine President Gloria Arroyo has pleaded not guilty to electoral fraud before a court in Manila.

She was escorted under tight security to court from a military hospital where she is being detained while undergoing treatment for a spine condition.

She was arrested in November 2011 after trying to leave the country to seek medical treatment.

Mrs Arroyo is accused of rigging a 2007 election in favour of her candidates.

Prosecutors say she helped a powerful local clan leader rig senatorial elections in a southern region where 12 candidates she backed swept to victory.

The poll rigging charge is the first of several cases expected to be brought against her.

The trial is seen as a landmark case in the country and a test for her successor, President Benigno Aquino III, a reformist who has promised to weed out corruption.

Mrs Arroyo insists that Mr Aquino is waging a personal vendetta against her, says the BBC's correspondent in Manila, Kate McGeown.

Mrs Arroyo, herself the daughter of a former president, has been surrounded by corruption allegations for years, and survived several attempts to have her impeached while in office.

If convicted Mrs Arroyo, who was president from 2001 to 2010, could face life in prison. But it could be some time before the verdict is known.

Trials in the Philippines take a long time, says our correspondent. Mrs Arroyo's predecessor Joseph Estrada's trial for corruption lasted six years.

Her husband, Miguel "Mike" Arroyo, delivered a short statement to reporters at the court, saying that his wife "feels the case is an injustice".

He maintained that she is still suffering from back pain that requires medical treatment abroad.