By Clement Uwiringiyimana

KIGALI (Reuters) - Two Rwandans extradited from the Netherlands to their home country pleaded not guilty during a preliminary court hearing in Kigali on Monday to crimes committed during the 1994 genocide.

Jean Baptiste Mugimba and Jean Claude Iyamuremye face charges of genocide, conspiracy to commit genocide, complicity in genocide, murder as crime against humanity, extermination as a crime against humanity, and the formation of criminal gang.

Mugimba faces an additional charge of incitement to commit genocide. Both men were arrested in the Netherlands, where they had been living, and flown to Kigali on Nov. 12.

Ethnic Hutu extremists killed more than 800,000 Tutsis and politically moderate Hutus in a three-month rampage in 1994, after unknown gunmen shot down a plane carrying the then-presidents of Rwanda and Burundi.

Prosecutors say Mugimba, 57, is a former secretary general for the Coalition for the Defence of the Republic, an extremist Hutu political party.

Iyamuremye, 40, is suspected of having been a local leader of the Interahamwe militia and a member of the National Revolutionary Movement for Development, the ruling party at the time of the genocide.

After pleading not guilty, the men both asked for more time to prepare for the case against them. They will appear in court on Tuesday.

Rwanda says it has issued over 600 arrest warrants globally for genocide suspects still at large.

(Writing by Katharine Houreld; Editing by Tom Heneghan)