Iran's police force has dismissed the commander of a city in the northern province of Gilan after the death in custody of a detainee, state media said on Saturday.

Mohammad Mir Mousavi, 36, was arrested on July 22 after being involved in a fight in Lahijan, police said in a statement carried by the official news agency IRNA.

"The police commander... was dismissed due to insufficient oversight of the conduct and behaviour of staff," the police said.

"Due to the complexity of the matter, the final conclusion on the cause of Mohammad Mir Mousavi's death depends on the medical examiner's final report.

The police said the station commander and several officers involved in the incident had been suspended.

"The behaviour of some law enforcement officers was against the professional policy of the police and that is not acceptable in any way, so they were referred to the judicial authority," the statement added.

The Norway-based Kurdish human rights organisation, Hengaw, on Wednesday said Mir Mousavi "was killed under torture in the detention centre".

On Thursday, Iranian President Masoud Pezeshkian ordered an investigation into the case.

Dismissals of members of the security forces are rare in Iran.

In 2022, the death in custody of Mahsa Amini, a 22-year-old Iranian Kurdish woman who had been arrested in Tehran for an alleged breach of the country's strict dress code for women, sparked months of deadly nationwide protests.