Mauritania authorities have formally charged the leading opposition candidate in recent presidential elections, Mohamed Ould Haidallah, with plotting to overthrow the government.

Mauritania's state prosecutor says Mr. Haidallah has been charged with plotting to stage a coup against the government of President Maaouiya Sid Ahmed Ould Taya.

The leading opposition candidate was one of more than a dozen of his campaign workers and family members who were arrested in the days before and after the November 7 presidential election.

His adviser, Mohamed Ould Rashid, says that the allegations of a coup plot are unfounded.

He says it would not be rational for the front-running opposition candidate seeking to be elected to conspire to overthrow the government.

Mr. Haidallah had been briefly detained a day before the November 7 election, and again on Sunday. His release on the eve of the election was apparently calculated to allow the balloting to go ahead.

According to the Mauritanian constitution, the election could not have been held had any of the candidates been imprisoned on election day.

Incumbent President Maaouya Ould Sid Ahmed Taya was declared the winner of the presidential election with 67 percent of the vote. Mr. Haidallah, who obtained about 19 percent of the vote, denounced the elections as rigged and called for Mauritanians to take to the streets in protest.

Mr. Haidallah, a former president, took power in a 1979 coup, and was overthrown five years later by President Taya.

There has never been a peaceful, democratic transfer of power in Mauritania. Under international pressure, President Taya began a process of democratization in the 1990s, but presidential elections that have kept him in power since that time have widely been seen as flawed.