Belgium has sent in 180 soldiers to help with staff shortages in prisons affected by a strike for the last two weeks.
The army are to assist the police and the Red Cross who have been working in jails since the strike began.
Soldiers have already been deployed to three of the largest prisons affected, Lantin, Saint-Gilles and Forest.
Prison employees in Brussels and French-speaking Wallonia are on strike over staffing levels.
Ministers decided on Sunday to requisition the army “to provide additional humanitarian support” in the Brussels and Wallonia prisons, Le Soir reports.
Some inmates were not being given basic rights such as three meals a day, showers and family visits, it said.
Belgian Human Rights League President Alexis Deswaef said it was the first time the army had been used in a social conflict in Belgium.
Flaws in the prison system, caused by underinvestment, were at least partly to blame for increased radicalisation in Belgian jails, he said.
“There is no money for any social guidance, any psychological guidance, any religious guidance,” he told the BBC.
What’s gone wrong in Belgium’s jails? By Piers Scholfield, BBC News, Brussels
Belgium’s prisons have long been criticised for chronic overcrowding and dismal conditions for inmates.
Even before this latest strike, a report by the Council of Europe’s anti-torture committee condemned several establishments for allocating just 3 sq m (32 sq ft) of space to each inmate; many having to sleep on mattresses on the floor, and having buckets instead of toilets in the cells.
In the aftermath of the terror attacks on Paris and Brussels, there has been a focus on prisons as potential “incubators” of Islamic radicalisation.
Several of the attackers spent time incarcerated in Belgium long before they planned the attacks, among them Paris “ringleader” Abelhamid Abaaoud and Salah Abdeslam, who is now in custody in France.
As one of many measures introduced by authorities following November’s attacks in Paris, special wings are being set aside in certain Belgian prisons, specifically to house extremists.
The strategy is fraught with risk, says Alexis Deswaef.
“You put very radicalised people in together with moderates and in the end you get just the very radicalised,” he says. “It’s a factory for more radicalisation.”