The BBC says the Iranian government has started to block its citizens from viewing its Persian website, as hostilities escalate between Tehran and western governments over its decision to start a uranium enrichment programme.
The broadcaster says the level of traffic to the site from within Iran has “dropped sharply over the last three days”.
BBC Persian.com is the most popular BBC non-English language website, usually receiving about 30 million page impressions a month – with half coming from inside Iran.
A BBC correspondent within Iran reports that when entering the Persian site, a sign comes up saying "access to this site denied".
No official explanation has been given by the Tehran government over the matter.
Google this week launched a Chinese Google website, which adhered to local Chinese laws forbidding content that criticised the Chinese government.