Police said the man, aged in his 30s, was attacked and sustained an injury to his leg in the incident in Wimbledon, southwest London, on Friday afternoon.

Britain's National Union of Journalists (NUJ) said the victim was prominent British-based Iranian journalist Pouria Zeraati, who hosts a show on the Persian language television news network Iran International which is critical of Iran's government.

Police said his injuries were not believed to be life-threatening and he was in a stable condition.

"This cowardly attack on Pouria is deeply shocking, and our thoughts are with him, his family and all of his colleagues at Iran International," Michelle Stanistreet, the NUJ general secretary said in a statement.

In January, Britain imposed sanctions on Iranian officials it said were involved in threats to kill journalists on British soil.

Those officials were members of the Islamic Revolutionary Guard Corps (IRGC) Unit 840, which an investigation by ITV news in Britain said was involved in plots to assassinate two television presenters from Iran International in the UK.

"While we are keeping an open mind, given the occupation of the victim and our publicised concerns about the threat to employees of that organisation, the investigation is being led by the Counter Terrorism Command," Commander Dominic Murphy, the head of that unit, said.

"I must stress that, at this early stage of our investigation, we do not know the reason why this victim was attacked and there could be a number of explanations for this."

There was no immediate response from Iranian officials to the report.

British police and security officials have increasingly warned about Iran's growing use of criminal proxies to carry out attacks abroad.

They say there have been more than 15 direct threats to kill or kidnap dissidents or political opponents that were linked to the Iranian state apparatus over the last two years.

Australian Associated Press