The corporation said television and radio services had been affected from 1245 GMT Friday onwards by "heavy electronic jamming" which had become "progressively worse".
Satellite technicians had traced the interference to Iran, it said.
The satellites its uses in the Middle East to broadcast BBC Persian television to Iran were being affected, meaning that audiences in Iran, the Middle East and Europe would likely experience disruption.
BBC Arabic television and other language services had also experienced transmission problems, the corporation said.
"Any attempt to block BBC Persian television is wrong and against international treaties on satellite communication. Whoever is attempting the blocking should stop it now," said BBC World Service director Peter Horrocks.
"It seems to be part of a pattern of behaviour by the Iranian authorities to limit the reporting of the aftermath of the disputed election.
"In Tehran, (BBC world affairs editor) John Simpson and his cameraman were briefly arrested after they had filmed material for a piece," he added.
Iranian authorities on Sunday shut down the office of Arab news channel Al-Arabiya in Tehran for a week in the wake of the disputed election win by President Mahmoud Ahmadinejad, the channel said.
BBC Persian, launched in 1940, is one of the corporation's oldest non-English language services.
