Mulud Vall Siyida said on Tuesday the former president had submitted to the Constitutional Council "evidence of massive, gross fraud during the election".

The legal action comes two days after Wald Hidala received a five-year suspended sentence for plotting a coup against his rival in the poll, incumbent Muawiya Wald Taya.

Wald Taya last month won a third term in office to head the northwest African country, but the opposition has rejected the result and called for a new vote. Wald Taya received 67%, according to official results.

Wald Hidala, whom he ousted in 1984, was the president's closest challenger, collecting slightly under 19%, according to the official tally.

Hidala arrested

Wald Hidala was arrested twice - once before the poll and once right after the results were announced, accused of planning to overthrow the president.

The opposition says November's 
presidential election was rigged

His attorney said on Tuesday Wald Hidala had "announced his intention of appealing the (election) result the day after the election but was prevented from doing so in time. The law now permits him to do so, now that he is free".

An African rights group in Senegal on Monday condemned the sentence on Wald Hidala as a deliberate obstruction of democratic power amounting to a time bomb.

RADDHO said the former leader, his son and three other defendants had been victims of a political trial.
 
The rights organisation said the conviction for plotting a coup was nothing but a political muzzle that "blocks any possibility of achieving power in Mauritania by democratic and peaceful means and amounts to a delayed-action bomb."

Political rivalry

Eight of Wald Hidala's co-defendants were also convicted of plotting a coup. He was fined 400,000 ouguiyas ($1550).

The former president, who has vehemently denied the charges, will appeal the verdict to the Supreme Court.

Another one of Wald Hidala's lawyers charged on Sunday that the justice system had been "used for a political settling of scores" between Wald Hidala and Wald Taya.

Wald Hidala was toppled in a 1984 coup led by Wald Taya, with whom he had earlier mounted a coup to oust the country's first president Mukhtar Wald Dadah.