BISKRA - Ali Benflis, the main rival to ailing but favourite incumbent Abdelaziz Bouteflika in Algeria's presidential election, said Saturday his main opponent in the April 17 poll will be fraud.

"Fraud is my principal adversary," said Benflis who was beaten in the 2004 election by Bouteflika.

The two men had been close during Bouteflika's first five-year term between 1999 and 2004, before they split and Benflis was sacked as prime minister in 2003.

"It must be remembered that in 2004 fraud was victorious and democracy was the loser," added Benflis.

Bouteflika, standing against five other candidates, was re-elected in 2004 with 85 percent of the vote. Benflis came second with just six percent.

"This time, I have a system in place that will fight fraud, with 60,000 observers for 60,000 polling stations," Benflis said.

"They will be there to monitor and expose any instances of fraud," he said on the campaign trail in Biskra, 450 kilometres (280 miles) south of Algiers.

Benflis is Bouteflika's main opponent in the election, in which the serving president is conspicuous by his absence.

Nevertheless, the 77-year-old remains the firm favourite, despite being too sick to campaign and barely leaving home after a minor stroke confined him to hospital in Paris for three months last year.

A frail-looking Bouteflika appeared on state television on March 3, his voice barely audible, to announce he would seeking a fourth term despite concerns about his capacity to govern.

In a very rare demonstration of its size, thousands of people took to the streets of the capital on March 21, two days before campaigning began, to call for an election boycott in protest at Bouteflika's candidacy.

Analysts say the president's absence from the campaign is unlikely to make any difference in a country where previous elections have been marred by patchy turnout and opposition accusations of fraud.