Using an object that “looked like a pistol”, Peter Madsen threatened a prison employee to break out of the Herstedvester Prison, penitentiary director Hanne Høgh Rasmussen told reporters.

Madsen then jumped into a white van and forced the person behind the wheel to drive several hundred metres before the vehicle was stopped by police.

Police said they were investigating the driver but did not for the moment consider him to be an accomplice.

Police were able to handcuff Madsen but because he was wearing what appeared to be a bomb belt, police backed away and a standoff ensued for several hours while police waited for explosive experts to arrive, Copenhagen Vestegns police inspector Mogens Lauridsen said.

“There is nothing at this point to indicate that (the belt) contained explosives … We think it was fake,” Lauridsen said, adding that an investigation was underway to be certain.

Police finally hauled Madsen away after more than two hours.

Armed police surrounded convicted murderer Peter Madsen after he attempted to escape from prison. Photo: Nils Meilvang/Ritzau Scanpix

Rasmussen meanwhile refused to comment on media reports that the prison employee was a female psychologist and that Madsen had taken her hostage.

The Herstedvester Prison is a high security facility with space for 161 inmates in need of psychiatric or psychological care, and for sex offenders.

Inmates are not typically locked up all day, a prison spokeswoman told AFP, refusing however to comment on Madsen's particular case.

Prison officials were tight-lipped about the details of how Madsen was able to break out.

“This is a closed prison. We are examining our security procedures to see if they have been respected and if they need to be reinforced,” Rasmussen said.

Police inspector Lauridsen said Madsen had not yet been questioned.

“He will be soon though,” he added.

Photos from the standoff scene showed Madsen sitting on the grass by a leafy wall next to a road a few hundred metres from the prison in a residential area, with police officers lying prone on the ground pointing their weapons at him.

READ ALSO: Danish submarine killer arrested after failed prison escape

Madsen, a 49-year-old amateur engineer, was convicted in April 2018 of murdering 30-year-old award-wining journalist Wall as she interviewed him on board his submarine in August 2017.

In a documentary that aired in September, he confessed for the first time to the killing, after having insisted during the trial that her death was an accident.

“There is only one who is guilty, and that is me,” Madsen said in the documentary.

Madsen had changed his version of events several times after his arrest and throughout his trial.

Psychiatric experts who evaluated him for the court found him to be “a pathological liar” who poses “a danger to others” and who was likely to be a repeat offender.

He will appear at the district court in Glostrup on Wednesday morning over the attempted prison escape, the prosecution service for Copenhagen Vestegn police confirmed on Twitter.

The hearing will take place behind closed doors, meaning that details of police evidence and any response by Madsen during the hearing will not be public or available to the press.

He is serving a life sentence for the murder of Wall, considered to be the strongest punishment in the Danish criminal justice system. A life sentence generally means a person will remain in prison for the rest of their life. As such, Madsen cannot be given an extra punishment for the attempted prison escape.

But the incident could affect the conditions under which he will serve his sentence in future, according to John Hatting, national chairperson of the Danish Prison and Probation Association (Kriminalforsorgsforeningen). The association represents prison employees including teachers, social worker and psychologists.

“He will get far fewer freedoms internally in prison. His opportunities for participating in the available activities will be subject to all security controls,” Hatting told Ritzau.

“It will simply be a crappy sentence for him. My assessment is that he will have a raw, boring sentence for a long time from now,” the prison employees’ representative added.

Hatting also said it would be “a number of years” before a return to the Herstedvester prison from which Madsen escaped could “even be considered”.

Moving a prisoner to another prison after an attempted escape was standard practice, he also said.

“There can be a lot of unspoken things, a psychological game between inmate and staff… so it’s part of the normal, professional response to an escape that you don’t return to the same things,” he said.

Several other Danish prisons are equipped to accommodate a life-sentence prisoner such as Madsen, according to Hatten. These include the Storstrøm, Nyborg and Ennermark prisons.

“They are used to organised criminals, biker gang members and other hardened criminals,” he said.