A German “serial killer” confessed after nearly 20 years on the run to murdering three boys, police said yesterday as they attempted to link him to further slayings in France and The Netherlands.

The 40-year-old German known as the “masked man”, who had worked as a youth group leader and had already been questioned in the case four years ago, admitted to killing boys aged eight, nine and 13 between 1992 and 2001.

He also confessed to sexually abusing “several” minors. Police suspect him in more than 40 cases.

“Neighbours described him as socially inconspicuous, nice, helpful, neatly dressed, reserved and intelligent,” chief profiler Alexander Horn told reporters.

The man, who was not identified, told investigators after his detention Wednesday in Hamburg, northern Germany, that he drove one of his victims to Denmark and buried his body in a sand dune.

Authorities said they believe he also killed an 11-year-old French boy, Jonathan Coulom, who disappeared from a camp in western France in April 2004 and whose body was recovered six weeks later.

And he is a prime suspect in the death of 11-year-old Nicky Verstappen in 1998 in The Netherlands, although he has denied involvement in either case.

“We want to determine whether we are aware of all of this man’s deeds or whether he may have committed other crimes,” the head of the regional police investigation unit spearheading the case, Karsten Lemke, said.

The unit was established to hunt the killer of a nine-year-old called Dennis, who vanished during a school field trip on September 5, 2001.

Mushroom pickers discovered his lifeless body about 40 kilometres away two weeks later but the killer’s trail had long gone cold.