A Greek national living in Munich was charged Friday with assisting Iranian intelligence in targeting a U.K.-based journalist at the Persian-language broadcaster Iran International.
Danish authorities separately announced that Iran had become an increasingly significant source of terrorist threat in Europe.
Ioannis Aidinidis, 46, was charged with an offense under the U.K.'s National Security Act following an investigation by Counter Terrorism Policing London. He was arrested in West Sussex on May 16 and has been in custody since.
"The country to which the allegations relate is believed to be Iran and the allegations relate to the targeting of a UK-based journalist working for Iran International," the Metropolitan Police said in a statement.
Aidinidis was due to appear at Westminster Magistrates' Court on Friday.
Police said there was no belief that there was any wider threat to the public.
"We know this may cause concern for many people here in the UK, and particularly those working in Persian-language media. We continue to work closely with a number of organizations and individuals to provide them with advice and support around their safety and security, and this includes the specific individual and organization linked to this investigation," Commander Helen Flanagan, head of Counter Terrorism Policing London, said.
"If anyone has concerns around their safety then they can contact their local police force and further advice and support can be provided," Flanagan concluded.
The London charge came on the same day Denmark's national security and intelligence service, PET, said Iran had emerged as an increasingly significant component of the terrorist threat facing the country.
PET head Finn Borch Andersen said Denmark's overall threat level remained at four on a five-point scale, but that in recent years the nature of threats had "changed significantly in character."
"Over the past year state actors have become increasingly important to the terror threat. We assess that this applies in particular to Iran, which poses a threat especially to Israeli and Jewish interests as well as certain Iranian dissidents in Europe, including Denmark," Andersen said.
"The threat from Iran emanates from the Iranian intelligence services, which make use of both criminal networks and the recruitment of operatives in Europe to plan and carry out attacks," he added.
In neighboring Sweden, the Swedish Security Service, Sapo, has also accused Iran of using criminal gangs to carry out "acts of violence" against Israeli interests and Iranian opposition figures, a claim Iran has denied.
A shadowy group believed by analysts to have links with pro-Iranian networks claimed responsibility this year for a string of arsons and other incidents targeting Jewish communities in Western Europe.
A member of the group told CBS News in March that it would "keep threatening U.S. and Israeli interests worldwide until we've avenged every child in Gaza, Iran, Lebanon, and the resistance nations."