Twelve activists for the main opposition candidate in Rwanda's presidential election, the first since the 1994 genocide, were in police custody yesterday accused of plotting "acts of violence" during the polling.

Some four million voters, about half the population, are due to vote in today's election, which the incumbent President Paul Kagame is tipped to win.

Kagame, 46, has effectively held the reins of power in the central African state since 1994 when his then Tutsi rebellion, the Rwandan Patriotic Front (RPF), took power, putting an end to the genocide that claimed the lives of a million Tutsis and moderate Hutus.

The camp of the main opposition candidate, Faustin Twagiramungu, has repeatedly denounced threats and intimidation against his supporters in the run-up to today's vote, the first multi-party election since independence in 1962.

Twagiramungu, 58, a moderate Hutu and former Prime Minister, told a press conference, and police confirmed, that 12 of his supporters were arrested Saturday, while two fled.

Police spokesperson Tony Kuramba said they were arrested for holding "an illegal meeting" and charged: "They were busy coordinating acts of violence in all the provinces for tomorrow (Monday)".

He added that one of the men arrested was a demobilised soldier.

Twagiramungu served as prime minister from 1994 to 1995 in the national unity government put in place by the RPF.

He returned home in June after eight years of self-imposed exile to accuse Kagame's camp of monopolising power in Rwanda.

Also yesterday the only woman presidential candidate, Alivera Mukabaramba, announced she was withdrawing from the race and threw her weight behind Kagame.

Twagiramungu's campaign manager said the withdrawal would "change virtually nothing" since Mukabaramba "had no weight as an opponent".

Her withdrawal leaves Jean-Nepomuscene Nayinzira as a maverick candidate, tipped to place a distant third in the polls.

The electoral campaign has been lopsided, with large-scale RPF rallies drawing crowds of thousands sporting Kagame baseball caps, T-shirts and sun umbrellas, and pro-Kagame songs blaring out of loudspeakers, while the other candidates' efforts paled into insignificance.

Simmering tensions rose a notch further on Saturday night after Chrysologue Karangwa, the head of the Electoral Commission, accused Twagiramungu's camp of "plotting" to "rig" the elections.

Twagiramungu promptly announced his camp would not station observers in polling stations today so the authorities would not be able to accuse him of cheating or interference.

Twagiramungu's campaign manager Ismael Mbonigaba said: "Fear is setting in in the ranks of the RPF. They risk losing the elections despite all the financial means they've put into them," he added.

"There are a lot of people who support Twagiramungu but who are afraid to say so in public. But today those people are going to vote," Mbonigaba said.

But the RPF dismissed the opposition threat yesterday.

"They can see that the wind has turned against them. They're looking for pretexts," said Modeste Rutabayiru, who organised Kagame's campaign rallies.

"Rwandans don't see politics along ethnic lines anymore," he added.

Last Wednesday the US issued a statement expressing concern over reports of "intimidation, harassment and the use of ethnicity as a means of inciting political division".

In recent months, several people close to the opposition have disappeared.

Monday's vote comes almost a decade after the 1994 genocide, planned and perpetrated by the Hutu-dominated regime then in power.

Since the genocide Rwanda has officially abolished ethnic categories.

Yet many people carry in the back of their minds the disastrous aftermath of the 1993 multi-party general elections in neighbouring Burundi, whose ethnic makeup, a Hutu majority and a Tutsi minority, is identical to Rwanda's.

Burundi's outgoing president Pierre Buyoya, a Tutsi, had been tipped to win. But in the first round of voting Melchior Ndadaye took some 65% of the vote, becoming the country's first democratically elected president and its first Hutu president, only to be assassinated four months later by the Tutsi-dominated army.

The killing triggered the civil war that is still going on in Burundi, ten years and some 300 000 lives later.

"On that day, even if Buyoya had had a Hutu domestic servant standing against him, the servant would have won," commented an African diplomat based in the region. – Sapa-AFP.