The prison inmate who

murdered two police officers and a bystander

in Belgium while on a two-day prison furlough was a “soldier of [ISIS’s] caliphate,” the terror group claimed on Wednesday.

ISIS’s Aamaq news agency said Benjamin Herman’s attack in Liège was an answer to its calls asking followers to target countries fighting against them.

Before Tuesday’s attack, Herman, who was gunned down by police, also killed a man with whom he had done time in prison by bashing his head in with a hammer.