Dutch crime boss Willem Holleeder, who is serving a life sentence in a maximum security prison in Vught, stayed at a Leiden hospital for three weeks following a heart operation, prompting questions about the extra-mural treatment of high-risk criminals who are seriously ill.

Holleeder (65), who has served 10 years of a life sentence for ordering five contract killings, was secretly taken to the Leids Universitair Medisch Centrum (LUMC) for the complicated procedure because it could not be done at the Scheveningen penitentiary hospital, a source at the hospital told the Telegraaf.

A plainclothes security unit from the prison was with Holleeder during the entire three weeks, the Telegraaf was told, only changing into uniform once inside so as not to alarm patients and staff. According to the source, Holleeder has “toasted cheese sandwiches for breakfast which he shared with the security officials”.

The revelation has prompted questions from police and the public prosecution office about how to handle criminals with a high flight risk who need specialised medical care.

VVD MP Ulysse Ellian said there was a reason Holleeder was locked up in high-security unit, and said caretaker legal protection minister Franc Weerwind should explain the circumstances of Holleeder’s stay at the hospital.

“I want to know exactly what the security was like and if he had visitors and could have smuggled out messages,” Ellian said.

He also wanted assurances that none of the criminals in the high-security prison in Vught could contact each other, he said.

Holleeder has a history of heart trouble. In 2007 his trial had to be stopped for him to undergo heart surgery. He later said he had had seven heart attacks and had a “do not resuscitate” notice in his cell.