Iran has reportedly blocked Google's Gmail service to the country to encourage citizens to use a national e-mail service instead.
The move is seen as an attempt to give the government more control over how Iranian citizens communicate over the internet.
The apparent shutdown of Gmail also coincides with efforts to deter any anti-government protest planned to mark the 31st anniversary of the Islamic Revolution on 11 February.
Iran has a history of blocking internet communication services that are perceived to threaten the Islamic regime.
Google has confirmed Gmail access problems in Iran, but did not comment on the role of Iranian authorities or the possible cause of the outage, according to US reports.
Google also did not say if the recent launch of Google Buzz, which added social networking capabilities to Gmail, may have contributed to Iran's move.