In April 1994, the Rwandan president and his Burundian counterpart were killed after their plane was shot down. The double assassination was the only kindling needed to ignite tensions between Hutus and Tutsis.
Hundreds of thousands of Tutsis and moderate Hutus were slaughtered.
By July, the killings had stopped when the Tutsi government took control and 120,000 people were detained for their suspected part in the violence,
The U.S. was deeply criticized for its inaction in Rwanda in 1994 that has been a black mark on its diplomatic history. Former U.S. President Bill Clinton said in March 2013 that his decision not to intervene in Rwanda was one of his biggest regrets.
"If we'd gone in sooner, I believe we could have saved at least a third of the lives that were lost...it had an enduring impact on me."
Hutus and Tutsis now live side-by-side in the country peacefully but new tensions have emerged. Many opposition politicians have been killed, jailed, or fled the country.
"I will encourage the people and Government of Rwanda to continue promoting the inclusive spirit needed for healing and reconciliation, and to deepen respect for human rights," said UN Secretary General Ban Ki Moon in a statement about the anniversary.
[Bahrain News Agency]