Security officials in Iran have raided at least four newspapers and arrested several journalists in what appears to be concerted action aimed at intimidating the media in advance of the presidential elections in June.

Sources in Tehran said reformist newspapers Etemaad, Shargh, Bahar and Arman were targeted by a group of plain-clothes officials who ransacked offices, filmed staff, confiscated documents and held several journalists.

When the Guardian phoned journalists at Etemaad and Bahar in the evening, officials were still present in the offices and editors of the two newspapers could not be reached. Etemaad's editor-in-chief, Javad Daliri, was reported to be among at least 10 journalists who have been arrested.

The semi-official Mehr news agency confirmed that a number of journalists have been arrested and said that officials were holding arrest warrants issued by judicial authorities.

Others reported to have been arrested include Sassan Aghaei, Nasrin Takhayori, Pourya Alami, Emili Amraee, Pejman Mousavi, Saba Azarpeik, Narges Joudaki, Motahareh Shafiee and Akbar Montajebi. It not clear where they have been taken, nor if more journalists have been detained. Journalists from the reformist Aseman weekly have also been arrested, according to Mehr.

According to Kaleme, a website close to opposition leader Mir Hossein Mousavi, two other journalists were also arrested on Saturday. They were named as Milad Fadayi-Asl, the political editor of the Iranian Labour News Agency and Suleiman Mohammadi, a reporter from the reformist Bahar newspaper. Both are reported to have been taken to Tehran's Evin prison.

Reasons behind the mass arrests on Sunday are still not clear but Mehr said the journalists were accused of co-operating with "anti-revolutionary" Persian-speaking media organisations outside the country. Iran has previously arrested people who it claims had links with foreign-based Persian-speaking media, especially the BBC's Persian service, which is loathed by the Islamic republic but remains popular in the country.

Also on Sunday, judicial officials ordered the filtering of Tabnak, a popular conservative news website close to former presidential candidate Mohsen Rezaee. The arrest of journalists in Iran is not only limited to those close to the reformists. President Mahmoud Ahmadinejad's media adviser, Ali Akbar Javanfekr, was given a six-month prison term in September.

According to the New York-based Committee to Protect Journalists (CPJ), Iran is currently the world's second-worst jailer of journalists, with 45 behind bars

Iranian journalists working in exile have not been immune from the crackdown, nor foreign media inside the country. Some exiled journalists have complained that their family members in Iran have been repeatedly harassed and summoned for questioning. Last year, Iran closed down Reuters' office in Tehran and at least one of its staff was subjected to interrogation.

"The situation for independent journalists is Iran is worsening by the day," CPJ's deputy director, Rob Mahoney, said in October. "High-profile persecutions and imprisonments are an attempt by the authorities to intimidate the media into silence and self-censorship. The international community must speak out against such actions."