"Rwandan voters have the freedom to decide," Kagame told his Rwandan Patriotic Front supporters at a rally at the Kigali national stadium.

The rally was estimated to cost $2 million. However, campaign co-coordinator Christophe Bazivamo said the funding was supplied by "voluntary contributions".

The more modest Social Democratic Party of Deputy Speaker Jean-Damascene Ntawukuriryayo is planning to take out a bank loan.

Two other presidential challengers – the Liberal Party's Prosper Higiro and the Party of Progress and Concord's Alvera Mukabaramba – will also be campaigning on low budgets.

Those three parties supported Kagame during the 2003 presidential election and are described by the opposition as the RPF's "political satellites".

But the three main opposition parties that had planned to contest the election are already practically sidelined.

The Unified Democratic Forces has not been officially registered by the authorities and its leader, Victoire Ingabire, has faced legal action since April after being accused of negating the genocide and abetting terrorism.

The Social Party (Imberakuri) faces similar problems and its leader Bernard Ntaganda has been behind bars since June 24.

In another development, Andre Kagwa Rwisereka – vice chairperson of the unregistered opposition Democratic Green Party – was found dead, nearly decapitated, on July 14.

Several senior army officers have been arrested in recent months and one general, Faustin Kayumba Nyamwasa, narrowly survived an assassination attempt in exile in South Africa.

An opposition journalist who claimed to have uncovered the regime's responsibility in the attempted murder was shot dead days later.

Kagame's government has flatly denied any involvement in the killings.

"There have been all kinds of activities... which have been orchestrated in order to instill a climate of fear in the run-up to the elections but also in an attempt to smear the government," Foreign Minister Louise Mushikiwabo told AFP in a recent interview.

Restricting political and press freedom

Rights groups have repeatedly accused Rwanda of restricting political and press freedom ahead of the election.

Kagame has often been praised by Western countries for his economic vision and his ability to maintain stability in genocide-scarred Rwanda but the latest outbreak of political violence appeared to cause some unease.

UN Secretary General Ban Ki-moon "expressed his concerns regarding the recent incidents which have caused political tensions" and demanded a full investigation into the death of the journalist and Rwisereka's murder.

Ban's statement came last week in Madrid, where Kagame was invited to talk on the status of the Millennium Development Goals.

Spanish Prime Minister Jose Luis Rodriguez Zapatero opted out of a meeting with Kagame at the last minute following protests from some political parties over the Rwandan president's role in the genocide.