“This is serious,” Anja Neumayer, the station commander told news agency TT.

The 22-year-old man, who heads up the Red & White Crew, a criminal wing of the Hells Angels biker gang in Sweden, was left unattended in a five metres squared exercise yard with only light netting overhead.

“He somehow managed to get himself up and through the netting. It isn’t that strong so if you’re able to climb and jump it’s not impossible,” said Neumayer.

“This is an old building, built with older security features than those used now.”

According to police, the Red & White Crew, a so called biker gang “supporters group” which runs a number of criminal rackets in Sweden, has grown rapidly in numbers in recent years.

Police in Nörrköping searched for the gang’s leader on Saturday night but suspect that he may already have escaped overseas.