The murder this week of a security guard at a Belgian nuclear research centre is a purely criminal affair unrelated to any terrorist threat, prosecutors said Saturday.

The Charleroi prosecutor's office in charge of the case "formally denied" any connection between the murder of Didier Prospero, who was shot dead on Thursday at his home in Froidchapelle and a planned terror attack, the Belga news agency reported, citing the prosecutor.

There was no immediate independent confirmation from the prosecutor's office in Charleroi, about an hour's drive south of Brussels.

Belga said the prosecutor had also denied media reports that Prospero's access badge had gone missing.

Prospero, who worked for the G4S security firm, was found dead in his bathroom by his three children when they returned from school. He had been shot with four bullets.

His dog was also killed.

He was in charge of security for a nuclear research centre at Fleurus. Media had said he worked at a nuclear power plant.

The case is being handled by criminal investigators and terror specialists are not involved, Belga said.

The media reports follow last year's discovery by investigators of surveillance footage of an official from a Belgian nuclear plant that was found in the flat of a suspect linked to the Brussels and Paris attacks.

Belgium's nuclear plants face threat of cyber-attack: EU counter-terror chief
Brussels (AFP) March 26, 2016 - Belgium's network of nuclear power plants and other major infrastructure face the threat of a cyber-attack over the next five years, the European Union's counter-terror chief said in an interview published Saturday.

"I would not be surprised if there was an attempt in the next five years to use the Internet to commit an attack," Gilles de Kerchove told daily La Libre Belgique.

"It would take the form of entering the SCADA (Supervisory Control and Data Acquisition), which is the nerve centre of a nuclear power plant, a dam, air traffic control centre or railroad switching station," he added.

His concerns come as Belgium is on high alert following Tuesday's suicide bombings at Brussels airport and aboard a metro train that killed 31 people and injured some 300.

Belgium's neighbours have raised concerns over the country's creaking nuclear plants for some time, after a series of problems ranging from leaks to cracks and an unsolved sabotage incident.

Doel 1, the country's oldest reactor, was originally shuttered in February 2015 under a law calling for the country's gradual phasing out of nuclear power, but the government then restarted it under an extension deal.

According to reports, a security guard at a Belgian nuclear power plant was murdered Thursday and his access badge stolen. Officials were not immediately available to comment.

These reports follow the discovery by investigators last year of surveillance footage of a Belgian nuclear plant official in the flat of a suspect linked to the Brussels and Paris attacks.