Police in Peru say Dutchman Joran van der Sloot has confessed to killing a young Peruvian woman in a hotel in the capital, Lima, on 30 May.
Peru's chief police spokesman Col Abel Gamarra told the Associated Press news agency Mr van der Sloot had admitted to the killing under police questioning.
Stephany Flores Ramirez's body was found in his hotel room, police say.
Mr van der Sloot was arrested but never charged over the 2005 disappearance of Alabama teenager Natalee Holloway.
The investigation into her disappearance on the Caribbean island of Aruba gained significant media coverage in the US and elsewhere around the world.
Mr van der Sloot's alleged confession to killing Ms Flores, 21, came on his third day in their custody, Peruvian police said.
The Dutchman is reportedly seeking to hire his own lawyer. He has not commented publicly on the allegations against him.
Police released video on Saturday taken from hotel security cameras that appeared to show Ms Flores entering Mr van der Sloot's hotel room with him at 0500 local time (1100 GMT).
The video apparently shows him leaving alone about four hours later.
Mr van der Sloot was arrested by police in Chile on Thursday after entering the country on 31 May.
He was then brought to Peru on Saturday in a police convoy from Chile.
Mr Gamarra said Mr van der Sloot would now be assigned to a prison while prosecutors prepare formal charges.
Mr van der Sloot is believed to have entered Peru on 14 May to play in a poker tournament.