The Intelligence Ministry said in a communique published in newspapers on Monday that three senior members of the small Iran Nation Party (INP) had been in custody since the outbreak of street riots in Tehran in mid-July, following pro-democracy demonstrations.
It identified the three as Khosrow Seif, Bahram Namazi and Farzin Mokhber. Another activist of the movement, Mehran Abdolbaqi, is also in detention, the ministry said.
"Among other things, they provoked and excited rioters and raised delusional slogans against sacred (values). They also had continuous contact with foreign (sources) and transmitted news, distorting facts, and granted interviews to foreign media," it said.
Namazi had been serving as INP's leader since the death of its founder Dariush Forouhar and his wife Parvaneh in a chain of murders of dissidents and intellectuals late last year.
The murders were committed by "rogue" elements within the secret service, a development which led to the resignation of intelligence minister Qorbanali Dorri Najafabadi and calls for a structural revamp of the secret service.
The ministry, trying to keep a low profile since the exposure of its role in the murders, bounced back after the riots, leading the campaign against opposition activists with alleged foreign links.
It has been regularly issuing communiques, revealing names of some of those arrested and exposing their alleged role in the unrest.
The ministry said it was also holding a number of other activists ranging from Islamic liberals to "anti-revolutionary" communist sympathisers.
Among those arrested is Hassan Zarezadeh, a member of the Guild of Students and University Graduates, led by maverick opposition activist Heshmatollah Tabarzadi.
Tabarzadi, an Islamic militant turned radical reformer, has been in jail for weeks for insulting the Islamic system in his now-banned newspaper Hoviat-e Khish.
"In Tabarzadi's absence, his group has been issuing contradictory statements in a bid to disturb public opinion and destroy the general atmosphere of the press and universities," the communique said.
"In recent days their office had been made into a safe haven for dissidents...There they received recommendations from foreigners and counter-revolutionaries."
It said Zarezadeh, who had campaigned for freedom of political prisoners, had a major role in such activities, transmitting news abroad to be "exploited" against the Islamic republic.
"For example, such reports prompted foreign media, notably American radios (in Farsi) to make investments in this regard...Their false reports were used as a tool to portray a negative image of the Islamic republic," it said.
The ministry also accused the group of seeking financial help from foreigners, notably the U.S. Radio Liberty, based in Prague.
Iran's special clerical court on Sunday found the publisher of the leading pro-reform newspaper Salam guilty of printing classified material and defamation.
