Paul Kagame (R) led the forces that stopped the killings in 1994
Rwanda's President Paul Kagame has said a Spanish judge who issued arrest warrants for 40 Rwandan army officers can "go to hell".
Mr Kagame described judge Fernando Andreu as "arrogant".
Judge Andreu accuses the officers of carrying out killings during Rwanda's genocide in 1994.
Mr Kagame said Judge Andreu had not distinguished between genocide perpetrators, and those who stopped it, such as his own forces.
The judge issued the arrest warrants in February, accusing the officers of genocide, terrorism and crimes against humanity.
He investigated the matter after a human rights group filed a complaint.
Under Spanish law, a court can prosecute alleged human rights crimes, even if they take place abroad.
Judge Fernando Andreu also indicted the Rwandan officers for the murder of nine Spanish citizens, including six missionaries.
He said he had evidence implicating President Kagame, who has immunity from prosecution.
"Imagine the arrogance involved - how can a Spanish judge sit in some town or village in Spain and sees it is his duty to indict the whole leadership of a nation," Mr Kagame said in Kigali.
In February the Rwandan foreign ministry called the warrants "bogus" and "ridiculous", and said the case was based on falsehoods, racist language and genocide denial.
The ministry said the judge had never visited Rwanda or the Democratic Republic of Congo, where some of the killings are alleged to have taken place.
Judge Andreu began considering the case in response to a complaint from a human rights group in 2005.
During a 100-day period in 1994, an estimated 800,000 Rwandans were killed, mainly ethnic Tutsis at the hands of radical Hutus.
The genocide came to an end when Tutsi-led rebels under Mr Kagame took control.
But the judge said that, after taking power, the army under Mr Kagame carried out mass killings of Hutus in Rwanda and in refugee camps in neighbouring DR Congo, then Zaire.
In 2006, a French judge, Jean-Louis Bruguiere, issued indictments against nine close aides of Mr Kagame, sparking a huge diplomatic row.