WikiLeaks founder Julian Assange has been arrested by officers from Scotland Yard's extradition unit.
The 39-year-old Australian was held when he attended a central London police station by appointment.
He is now expected to appear before a district judge at City of Westminster Magistrates' Court later today.
A Metropolitan Police spokesman said: "Officers from the Metropolitan Police Extradition Unit have this morning arrested Julian Assange on behalf of the Swedish authorities on suspicion of rape.
"Julian Assange, 39, was arrested on a European Arrest Warrant by appointment at a London police station at 9.30am.
"He is accused by the Swedish authorities of one count of unlawful coercion, two counts of sexual molestation and one count of rape, all alleged to have been committed in August 2010."
Sweden's prosecution authority said it had given British police all the information they requested, after a series of apparent legal hitches.
British media had reported that Assange was in Britain after WikiLeaks released a trove of cables exposing the inner workings of American diplomacy.
Assange's legal team has said it will mount a challenge in the British courts to any Swedish attempt to have him arrested and sent to Sweden.