Iran says it has arrested four people suspected of carrying out a string of assassinations at the request of a Kurdish fighter based in Britain.
"Iran's intelligence ministry says it has arrested four Britain-linked terrorists in the western city of Marivan, who carried out five assassinations in the last two years," state-run Press TV said on Thursday.
The report said the men were part of Komala, an Iranian Kurdish separatist group, which has been accused of carrying out attacks for decades in its bid for Kurdish autonomy.
It said the detainees received orders in the Iraqi city of Suleymaniyah from a commander who is now living in the UK, adding they were promised $20,000 for each killing.
The report did not say who their victims had been.
Kurds are an ethnic group with no state of their own. They make up large minorities in Iran, Iraq, Turkey, and Syria.
Iranian forces sometimes clash with Kurdish guerrillas who operate out of bases in northern Iraq.
According to Press TV, Iran's intelligence ministry said that Britain had "funded and supported certain terrorist groups against the Islamic Republic" and carried out secret espionage activities in the country.
However the British foreign office dismissed the story, saying it was the latest in a "long history of baseless Iranian allegations against the UK".
"The UK does not support or encourage terrorist activity in Iran, or anywhere else in the world," a spokesperson said in a statement.
"This claim will be seen as what it is; another long line of slurs against the United Kingdom from the government of Iran."
The news came as Iranians marked the 31st anniversary of the capture of former US embassy in Tehran, the capital.
Iran annually commemorates the capture of the building by Islamist students in 1979, months after the Islamic revolution which toppled the US-backed shah.
The embassy in central Tehran has remained closed and the US and Iran have had no diplomatic ties since then.