Allegations believed to be part of effort by Revolutionary Guards to undermine president's moves to improve contact with the west

Iranian judicial authorities have accused a group of recently jailed activists and bloggers of having links with the BBC and its past training courses.

At least 16 Iranian nationals, including employees of the technology website Narenji, were arrested in December in the southern province of Kerman as part of another crackdown by the intelligence forces of the elite Revolutionary Guards.

Half of those arrested have since been released on bail, the Guardian has learned, but the rest, including Narenji's staff, remain in detention.

The head of Kerman's justice department, Ali Tavakoli, alleged this week that those arrested had participated in projects run by the BBC and received funds deriving from London.

Iranian authorities have a deep suspicion of the BBC, especially its Persian service, which they accuse of having a political agenda, and have previously arrested people on charges of working or having links with the broadcaster.

"This gang was running a number of projects and plans for anti-revolutionary Iranians based abroad, especially for the BBC Persian under the guise of legitimate activities," he said during a press conference.

"Financial aid for this group was usually provided from London under the pretext of charitable donations. The director of the team was an individual who has served the BBC as a mentor and teacher in a number of countries such as Malaysia, India and Afghanistan and his travels to these countries was paid for by British intelligence services."

Tavakoli said that those held had confessed to "being tasked with fuelling social tension, spreading doubts and misrepresentations". It was not clear if the eight still in jail had access to lawyers or to their families.

He said: "They were consciously serving the plots designed by the sworn enemies of this country and they deserve to receive the most severe punishment."

The Guardian reported last year that the Iranian authorities had been conducting a smear campaign designed to discredit and intimidate London-based Iranian journalists working for BBC Persian.

A number of BBC Persian staff were victims of false allegations of sexual misconduct, duplicated Facebook accounts, and harassment of their family members in Iran including being summoned by the intelligence officials for questioning. The harassments have continued despite the election of Hassan Rouhani as president.

At least one of the detainees was among the trainees of an award-winning journalism development programme run by the BBC World Service Trust from 2006 to 2010, called ZigZag.

The BBC has denied that those arrested were co-operating with it and said the training programmes mentioned by the Iranian authorities ended four years ago, according to BBC Persian.

Soon after their arrests were made in Kerman, the semi-official Fars news agency, affiliated to the Revolutionary Guards, said the detainees has be in "contact with enemy media based abroad with the aim of producing content for educational websites targeted at citizen-journalists".

Bloggers and activists currently in jail include Aliasghar Honarmand, who is the founder of Narenji, which specialises in gadget news, Abbas Vahedi, Hossein Nozari, Reza Nozari, Amir Sadeghpour, Mehdi Faryabi, Ehsan Paknejad and Malihe Nakhaei.

A former BBC project manager, who did not want to be named, told the Guardian: "I believe the arrests, especially of the Narenji team, to be part of the reaction of the hardliners within the Iranian establishment to the attempts of President Rouhani to move towards the opening up of cyberspace and the media sphere; and to relax the previous rigid attitude towards contacts with foreign institutions."

The arrests have also coincided with attempts by the BBC to obtain stronger operational presence in Iran.

"As the Revolutionary Guards are opposed in general to improved contacts with the west; and in particular to developing contacts with foreign media outlets, especially the BBC, it seems they have revived an old and discredited story in an attempt to undermine the president's initiatives in this sphere," said the former BBC staffer.

"Additionally, after what have been in the eyes of the hardliners, unacceptable concessions by the government on the nuclear agenda, this could be part of a campaign to show that foreign policy compromises will not be matched by any accompanying liberalisation in the domestic sphere."