The European Union has called on Tehran to end its persecution of followers of Baha'i - a faith originating in Iran and which the government there views as heretical - and release its leaders from jail.
In a statement issued on Wednesday on behalf of the EU's 27 member states, the bloc's presidency expressed its concern at the May 14 arrests, reported dpa.
"The EU reiterates its serious concern about the continuing systematic discrimination and harassment of the Iranian Baha'is on the grounds of their religion.
"The EU calls on the Islamic Republic of Iran to uphold fully the right to adopt and practise a religion of choice, to end the persecution of the Baha'i community, and to release the detained individuals," the statement said.
According to reports, six senior members of the faith were arrested last week after Iranian Intelligence Ministry officers raided their homes.
The Baha'i website says the faith has been the subject of persecution in Iran since it was founded in 1844. It says the persecution became official government policy after the country's Islamic revolution of 1979, with more than 200 Baha'i adherents killed or executed since then.
The BBC says the Iranian government has denied detaining or executing people because of their faith.
In Iran there are an estimated 300,000 followers of the faith, which holds that the world's great religions all teach an identical truth.