Ten days to commemorate the Rwandan genocide 10 years ago began Sunday with the memory of massacre, as foreigners and locals visited churches where thousands were slaughtered and a conference heard a plea to end global indifference.

The international conference in Kigali opened Sunday afternoon, after participants had been shuttled to areas outside the Rwandan capital where some of the victims -- a total of at least 800,000 and up to one million -- were killed in 100 days in 1994.

At the churches in Nyamata and Ntarama, south of Kigali, some 15,000 people were massacred after they sought to take refuge there.

The cemetery of Nyanza, another stop on the tour on the outskirts of the capital, is the burial grounds for 3,500 people who were abandoned in a schoolyard by UN peacekeepers, and later massacred.

One Canadian visitor, Gerry Caplan, welcomed the harrowing tour.

"The more opportunities there are to explore -- not just the aspect of the bodies and the graves but also the background (to the genocide) -- the better," he said.

Hours later, the three-day conference, focussed on the hopeful theme of "preventing and banishing genocide forever", opened with a condemnation of international inaction.

"The international community could have kept the genocide from taking place," Francois-Xavier Ngarambe, the president of an association of genocide survivors, told the gathering.

The victims, he added, were "a people who meant nothing to the interests of the great powers".

Some 20 speakers are on the program for the conference, including President Paul Kagame, who was due to address the participants later on Sunday.

The Rwandan genocide was sparked by the assassination of the ethnic Hutu president, Juvenal Habyarimana, on April 6, 1994, whose plane was shot down as it came in to land at Kigali airport.

In a deliberate campaign of bloodletting, ethnic Tutsis and politically moderate Hutus were targeted from the following day, and only in July 1994 did a mainly Tutsi rebel movement led by Kagame seize Kigali and put an end to the carnage.

Remembering the events a decade on has sparked soul-searching in Kigali, among global powers who were silent witnesses to the carnage and at the United Nations, whose tiny contingent of peacekeepers in the central African country found itself helpless to act.

A coordinator of an organisation for students survivors of the genocide, Jean-Marie Vianney Usengimana, minced no words. "We are commemorating for the 10th time the genocide of the Tutsis of Rwanda. We remember how the international community abandoned us."

Among the historians, survivors, lawyers and genocide specialists on the conference roster, one of the most anticipated speeches will come Tuesday from Romeo Dallaire, the retired Canadian general who led the UN mission in Rwanda. He returned Friday to Kigali for the first time since his mission and the genocide.

A 1999 report laid the blame on UN Secretary General Kofi Annan and other UN officials, as well as on the United States and other Security Council nations, for failing to take action to stop the killing.

Other official events marking the anniversary will include a march in the capital Kigali on April 7, the date the killings began.

The same day, also in Kigali, a memorial in the district of Gisozi will be unveiled.

The official climax in the string of events is expected to be the formal ceremony in the Kigali stadium on Wednesday, which will be attended by eight heads of state or government and other foreign dignitaries.

Aside from former colonial power Belgium, no other Western state has sent its leaders - Sapa AFP.