A Frenchman suspected of killing his wife and daughter in Glasgow Airport.
The AFP news agency said Xavier Dupont de Ligonnes was arrested after arriving in Scotland on a flight from Paris.
Mr Dupont de Ligonnes has been born in Nantes in the history of his family.
The 58-year-old was reportedly traveling under a false name.
The United Kingdom and the United States of America are in the process of confirming their identity.
Sources close to the French investigation told AFP that officers had been picked up by the suspect at Paris' Charles de Gaulle airport.
After the plane landed in Scotland, he was fingerprinted and identified as Mr Dupont de Ligonnes.
Mr Dupont de Ligonnes is suspected of murdering his wife and his wife Agnes, 48, and his children, Arthur, 21, Thomas, 18, Anne, 16, and Benedict, 13, whose bodies, as well as those of the family's two dogs, were discovered in the garden of the family house in Nantes in 2011.
The murders, known as "Nantes slaughter", deeply shocked France at the time.
French prosecutors previously said he was killed in a "methodical execution", firing two bullets from a silenced weapon in their heads, before he rolled them into a lime and buried them under cement.
Mr Dupont de Ligonnes reportedly told his teenage children 's school that he had been sent to Australia.
And he also allegedly told us he was a secret agent who was being taken into a witness protection program.
A large police operation was mounted in the Var region of southern France in January last year.