Iranian President Hassan Rouhani's brother entered prison Wednesday to begin a five-year sentence after he was convicted of corruption, the semi-official ISNA news agency reported, citing his lawyer.

Hossein Fereydoun, who served as an aide to the president, was arrested in July 2017 and put on trial in February this year on allegations of financial violations.

In a final ruling, his sentence was reduced to five years from seven and he was ordered to pay a fine as well as bribes he was convicted of receiving, the judiciary said on October 1.

His lawyer said he entered Tehran's Evin prison on Wednesday.

"This morning Mr Fereydoun together with myself were present at the prosecutor's office," Hossein Sartipi said, quoted by ISNA.

"After legal procedures were completed, he was taken to Evin prison and was admitted to the prison," he added.

Fereydoun acted as a key adviser and gatekeeper to the president before his arrest.

The brothers do not share the same name because Rouhani changed his when he was younger to a word meaning "cleric".