"This is a serious decision and a unique problem in the recent history of the Belgian military," army chief Admiral Michel Hofman said at a press conference in Brussels.

Alongside Hofman, Minister of Defence Ludivine Dedonder described the behaviour as "unacceptable" and "in no way compatible with the values of the military".

An investigation was launched internally in November when a relative of a victim emailed Dedonder.

She said there was "humiliating and degrading treatment" including "battery and assault" and "harassment" with "threats, pressure and blackmail".

The officials said the hazing took place in a platoon within the 4th Engineer Battalion based in eastern Belgium and dated to 2021 according to preliminary evidence.

Investigations will seek to establish who was responsible among the "few dozen" people involved, who were pressured to keep quiet about it, Dedonder said.

"We are in a situation where perpetrators, victims and witnesses are mixed up," the minister said.

Hofman said the harassment took place during training. The officials gave no details of the acts but there was so far no indication of sexual or racist violence.

Some soldiers have been dismissed while others have been transferred but disciplinary measures will depend on the progress of the investigations, Hofman said.

"It takes time to put this puzzle together," he said.

Dedonder called on all Belgian soldiers, especially young recruits, to report any problematic behaviour they witness in the army.