"Mehdi Hajati, a member of this council, was arrested Thursday evening for supporting two people of the outlawed cult of Bahaism," IRNA quoted council presiding board member Ghasem Moghimi as saying.

Hajati, a reformist, had tweeted on Tuesday that "for the past 10 days, I did whatever I could to release the two Bahai friends that were arrested but failed".

"Our generation is tasked to not back down in reforming judicial processes and other things that endanger social justice," he wrote, also using a Persian hashtag that translating into English as "fair trial".

His twitter account, @MehdiHajati was suspended hours after his arrest.

Bahram Parsayi, a lawmaker from Shiraz, came to Hajati's defence on Thursday.

"Defending the civil rights of citizens should not be equated with supporting a cult," semi-official news agency ISNA quoted him as saying.

Parsayi also vowed to pursue the case through the judicial and security authorities.

Iran allows religious freedom for several minorities but targets the Bahai faith, which believes in unity among religions and equality between men and women.

The Bahai faith considers Bahaullah, an Iranian born in 1817, to be the latest prophet sent by God, in contrast with Islamic orthodoxy.

Bahais have been targets of persecution and discrimination in Iran since the emergence of the faith in the second half of the 19th century, well before the 1979 Islamic revolution.

The Islamic republic regards Bahais as "heretics" and suspects many of espionage for Israel, where the community has a centre in the northern city of Haifa.

The Bahai faith has an estimated seven million followers worldwide, including some 300,000 Iran where the community says they are barred from pursuing higher education and holding government jobs.