Rwanda begins 100 days of mourning for those killed in genocide 25 years ago

Photographs of those killed during the 1994 genocide are displayed at the Kigali Genocide Memorial Centre (Picture: EPA)

Commemorations have begun in Rwanda to mark the 25th anniversary of the genocide in which around a tenth of the population was massacred.

Crowds will gather on Sunday to begin 100 days of mourning, the time it took in 1994 for the murder of 800,000 Rwandans.

The ceremony marks the beginning of a week of events to honour the dead.

Rwandan President Paul Kagame is scheduled to lay a wreath at Gisozi genocide memorial site, where over a quarter a million of people are buried.

Rwanda's President Paul Kagame (R) welcomes Ethiopia's Prime Minister Abiy Ahmed who will attend for the 25th Commemoration of the 1994 Genocide (AFP/Getty Images)

In the afternoon, officials will join around 2,000 people in a "walk to remember" from parliament to the national soccer stadium, where candles will be lit in a night vigil.

At least 10 heads of state were expected to attend, Stephanie Nyombayire, head of communication at the president's office, told journalists on Saturday.

Canadian Governor General Julie Payette and European Commission President Jean-Claude Juncker were also expected.

The 100 days of slaughter began on April 6, 1994, after President Juvenal Habyarimana and his counterpart Cyprien Ntaryamira of Burundi - both Hutus - were killed when their plane was shot down over the Rwandan capital.

Flowers are arranged on top of mass graves where more than 250,000 people are buried (Getty Images)

The attackers have never been identified.

The attack mobilised Hutu government soldiers and allied extremist militia, who orchestrated the genocide to exterminate the Tutsi minority.

In villages across the densely populated country, neighbour turned on neighbour as men, women and children were hacked to death, burned alive, clubbed and shot.

As many as 10,000 people were killed daily. Seventy per cent of the minority Tutsi population was wiped out, and over 10 per cent of the total Rwandan population.

The fighting ended in July 1994 when the Rwandan Patriotic Front (RPF), a Tutsi-led rebel movement led by Kagame, swept in from Uganda and seized control of the country.

Official policy is to strongly discourage any talk of ethnicity, but the opposition says the tight control of the media and political sphere is also used to stifle dissent, something the government denies.

Additional reporting by Reuters.