The BBC's Chris Simpson: "The atmosphere is much less grim than last year"

Flags have been flying at half-mast throughout the country in memory of the three-quarters of Rwanda's Tutsi population, and many moderate Hutus, who died during the 13 weeks of killings.

Rwanda has completed its first elections since the slaughter

State-run Radio Rwanda invited people of all ages to spend the period reflecting on the genocide and promise that it will never happen again.

And the populace has been warned that there should be "no inappropriate revelry".

Footage, shot by the Information Ministry, of mass killings at roadblocks, schools, churches and stadiums is being shown at the Amahoro soccer stadium in Kigali.

The week of mourning will culminate in a mass reburial of the remains of 20,000 Tutsis who were killed on 14 April 1994, in Kibeho, 60 miles (100km) south of Kigali.

In the massacre, Tutsi men, women and children were encouraged by local authorities to seek shelter from Hutu mobs in the Roman Catholic church, but then found and killed in the church compound.

There will be other, smaller reburials across the country, as well as meetings and public debate on issues such as justice and reconciliation.

'Massive difficulties'

The genocide ended in July 1994, when Tutsi-led rebels of the Rwandan Patriotic Front won power and ousted the Hutu extremist government.

The group then formed a government including minority Tutsis and majority Hutus and embarked on a national unity programme.

More than 125,000 suspects have been jailed on suspicion of participating in the massacres, carried out by former Hutu soldiers, militiamen and ordinary civilians on orders of the extremist Hutu government.

The BBC's Chris Simpson, reporting from Rwanda, says the atmosphere is much more optimistic than in previous years, but the country still faces "massive difficulties".