A Rwandan militia leader has pleaded guilty to charges of genocide and crimes against humanity.

Omar Serushago was a leader of the Hutu Interahamwe militia in northwest Rwanda during massacres in 1994. He's the second defendant to plead guilty at the International Criminal Tribunal for Rwanda since it was set up four years ago.

Hutu extremists linked to Rwanda's former government carried out the massacres in a bid to exterminate ethnic Tutsis and moderate Hutus who opposed the genocide.

Serushago pleaded guilty to one count of genocide and three counts of crimes against humanity related to murder, extermination and torture.

He pleaded not guilty to a fifth count of crimes against humanity related to rape. That charge was then dropped. The tribunal has not set a date for sentencing.