LONDON, (Reuters) – A leading media watchdog has accused Iran of trying to cow journalists into silence and self-censorship, adding to international pressure on Tehran over its treatment of activists and the press.

The New York-based Committee to Protect Journalists (CPJ)said Tehran, which is facing tough international economic sanctions over its nuclear programme, was also trying to restrict internet access.

“The situation for independent journalists is Iran is worsening by the day,” CPJ Deputy Director Rob Mahoney said in a statement on Wednesday.

“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.”

The United Nations human rights office called on Tuesday for the immediate release of prominent activists and journalists arrested or intimidated in what it called an apparent clampdown on critical voices ahead of next year’s presidential election.

The CPJ expressed concern about Ali Akbar Javanfekr, press adviser to President Mahmoud Ahmadinejad and head of the state-run IRNA news agency, who was jailed for six months for insulting the Supreme Leader and Reuters Bureau Chief Parisa Hafezi on trial on charges of spreading lies and propaganda.

In citing a series of arrests of print journalists, it said Iranian authorities had maintained a ‘revolving-door’ policy, freeing some temporarily as they took others into custody.

In March, the Iranian government suspended the press accreditation of all Reuters staff in Tehran after publication of a video script on women’s martial arts training that erroneously referred to the athletes as “assassins”. Since then, Reuters has been unable to report from Iran.

Reuters, the news arm of Thomson Reuters, the global news and information group, corrected the script after the martial arts club complained and apologised for the error.

Reuters’ Bureau Chief in Iran, Iranian national Parisa Hafezi, was subsequently charged on several counts including spreading lies and propaganda against the establishment. Hafezi had not been involved in drafting the video script.

An Iranian jury voted on Sunday to convict the Reuters news organisation over the video script. A final decision will be made by a judge, expected to issue his verdict this month.