Claims that Britons have been arrested after protests in Tehran are being investigated by the Foreign Office, a spokesman said today.
Reports on Iranian state television said some British passport-holders had been detained following unrest sparked by the recent election.
A spokesman for the Foreign Office said: "We are aware of the reports and we will be looking into them."
Riot police and protesters clashed in the streets around Iran's parliament last night as hundreds of people converged on a Tehran square in defiance of government orders banning demonstrations.
It followed a declaration by the country's supreme leader that the government would not yield to the opposition.
Ayatollah Ali Khamenei accused the US, Britain and other foreign powers of being behind the street protests.
Iranian intelligence minister Gholam Hossein Mohseni Ejei also accused Britain of issuing propaganda against Iran.
Iranian television quoted Mr Ejei as referring to the "meddling of alien countries" and saying that one which "strongly propagated in its media against the Islamic Republic of Iran and some of its agents have been involved in Iran's tension is England".
The Foreign Office confirmed that it was aware of the case of a journalist with joint British and Greek nationality who was held in the crackdown at the end of last week.
The Washington Times reporter, believed to be Iason Athanasiadis-Fowden, known as Jason Fowden, was arrested as he was attempting to leave the country according to the Iranian news agency IRNA.
A Foreign Office spokeswoman said that they understood that Greek officials were providing consular assistance.
"We stand ready to help if needed," the spokeswoman said.
Downing Street said the British ambassador in Tehran, Simon Gass, had been in contact with his Greek counterpart about Mr Athanasiadis-Fowden's case.
The Prime Minster's spokesman said Mr Gass had also made a request to the Iranain ministry of foreign affairs for consular access.
'Little Satan' Britain accused over violence
Wednesday, 24 June 2009
Pro-government supporters in Tehran may continue to chant "death to America" but for Iran's leaders it is the "Little Satan" of Britain that is to blame for stirring up recent unrest.
Ayatollah Ali Khamenei described the UK as the "most evil" country during his address last Friday, precipitating tit-for-tat diplomatic expulsions between the two countries.
The reasons why Britain has been singled out for Iranian anger are a mixture of historic distrust, modern concerns and political realities.
The UK has long been accused of "meddling" in Iranian affairs. In 1941 British and Russian occupied the country and forced its ruler, Reza Shah, to abdicate in favour of his son.
The deposed Shah was then sent into exile, living out the last of his years in British territories.
Relations between the Iranian people and the UK deteriorated after the war.
In 1953, the British Government - angered over plans to nationalise Iranian oil production - instigated and then backed a CIA plot which saw popular prime minister Dr Mohammad Mossadegh removed from power.
Throughout the 1960s and 1970s, the UK supported the increasingly corrupt and repressive rule of Mohammad Reza Shah Pahlavi.
Since the Iranian revolution there has continued to be points of contention such as the fatwa handed down on author Salman Rushdie by Ayatollah Khomeini and the UK's involvement in Iraq.
But despite historic distrust, experts point towards more recent developments as to why Iran's leaders are reserving their most stinging criticism for London during the current unrest.
Top of these is the position of the BBC. Tehran has been angered by the launch of the broadcaster's Persian service at the beginning of the year.
Mehrun Etedari, research assistant at the Saban Centre for Middle East Policy at the Brookings Institute, explained: "The Iranian government has been especially hard on the new BBC Persian service, which it has categorised as propaganda of the British state.
"They see it as a big threat to the state control of broadcast media."
"Several months before the election, there was a government threat to anyone who co-operated with the BBC service."
In recent days, state media in Iran has paraded contrite "protesters" who claim that they were influenced by the BBC into rebelling.
A BBC correspondent is also among the foreign media expelled from the country since the contested election.
It may also be the case that Britain is a better target than the "Great Satan" of America for political reasons.
The US - a far greater influence in the region - is now in the hands of a president who has expressed a desire to engage Iran in negotiation.
By focusing anger on Britain as opposed to the US, Iran's leaders could be making sure that they do not force President Barack Obama to shut the diplomatic openings he has seemingly offered Tehran.
Mr Etedari said: "It is not as if the Iranian government is saying that only Britain is to blame for stirring up protest, they are also accusing the US. But Khamenei's harshest words have been for the UK.
"You could see it as the Iranian government leaving a bit of room open for negotiations with the US, especially considering the importance Obama has put on talks."