British police arrested Rwanda's intelligence chief as he was about to leave the country at the weekend, London news organisations report.

Karenzi Karake, head of Rwanda's national intelligence and security services, was arrested on a European arrest warrant issued by a Spanish court.

Karake was among 40 Rwandan military and political figures indicted by a Spanish judge in 2008 on charges of genocide and crimes against humanity.

The charges arose from massacres allegedly ordered in the 1990s after the Rwandan Patriotic Front had invaded Rwanda to end the 1994 genocide. Three Spanish NGO workers were among those killed.

The Canadian-based online news service, Digital Journal, reported last week that Karake was in Britain and that his presence was placing authorities in "a legal dilemma."

It quoted a police spokesman as saying: "As you can imagine this is a serious issue... With sensitive issues you have to be careful to make the right response that's accurate. We are not confirming or denying anything at this stage."

Late on Monday, news organisations including the BBC, the Guardian, the Telegraph and Reuters confirmed that Karake had been arrested at Heathrow Airport on Saturday.

The Spanish lawyer for victims in the case told Digital Journal that the Spanish judge had confirmed the arrest. "Interpol UK has requested Interpol Spain confirm that the European Arrest Warrant is still alive and pending. That was done by the Spanish judge. Now all documents required by the UK are being translated officially into English," he reportedly said.

Reuters reported later that police said Karake had appeared in Westminster Magistrates' Court. He will appear in court again on Thursday.