Hichilema, who took office last week, has been arrested over a dozen times during his political career and made restoring freedoms a linchpin of his electoral promises.
In a televised address to the nation, Hichilema on Sunday announced the appointment of the new army and airforce chiefs, as well as a new head of the southern African country’s defence wing.
“I am relieving all commissioners of police with immediate effect,” he added, without providing reasons for the replacements.
He also urged police to conduct thorough checks before detaining suspects, stressing that “no one should be arrested before investigations are concluded”.
Hichilema beat his long-term rival Lungu in August 12 polls by a landslide of almost one million votes — a victory hailed as a democratic milestone for opposition movements in Africa.
During his inauguration speech on Tuesday, he promised to crack down on political “thuggery” and repression, reassuring independent media they would no longer face tear gas or shutdowns.