LONDON (Reuters) - Five Rwandans accused of involvement in the genocide that killed 800,000 people in just 100 days were arrested in Britain on Thursday after an extradition request from Rwanda, London police said.

Emmanuel Nteziryayo, Charles Munyaneza, Celestin Ugirashebuja, Vincent Bajinya and Celestin Mutabaruka appeared at a London court under extradition warrants alleging genocide and murder, a police spokesman said.

Four of the five were freed by the High Court in 2009, overturning a ministerial extradition order because of fears they would not get a fair trial in Rwanda. They had been in custody since 2006.

During 100 days of slaughter in 1994, 800,000 minority Tutsis and politically moderate Hutus were killed.

Rwandan prosecutor general Martin Ngoga welcomed the arrests, which took place early on Thursday, and said he hoped London would follow the example of other jurisdictions that had extradited suspects.

"They are all suspects of genocide against Tutsis and crimes against humanity committed in Rwanda in 1994 ... Rwanda has made significant progress since 2009 when the British Courts rejected the extradition requests to Rwanda," he said.

The five men are due to appear at Westminster Magistrates court again on June 5.

(Reporting by Stephen Addison, Shadia Nasralla in London and Jenny Clover in Rwanda; Editing by Alison Williams)