BBC audiences in Iran, the Middle East and Europe may be experiencing disruption to their BBC TV or radio services today. That is because there is heavy electronic jamming of one of the satellites the BBC uses in the Middle East to broadcast the BBC Persian TV signal to Iran.

Satellite technicians have traced that interference and it is coming from Iran. There has been intermittent interference from Iran since Friday, but this is the heaviest yet.

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, John Simpson and his cameraman were briefly arrested after they had filmed the material for this piece. And at least one news agency in Tehran has come under pressure not to distribute internationally any pictures it might have of demonstrations on the streets in Iran.

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However, the availability of witness material from Iran is enabling international news organisations to be able to report the story. Viewers of BBC Persian TV have been in touch (in Farsi), sending videos, stills and providing personal accounts.

It is important that what is happening in Iran is reported to the world, but it is even more vital that citizens in Iran know what is happening. That is the role of the recently-launched BBC Persian TV which is fulfilling a crucial role in being a free and impartial source of information for many Iranians.

Any attempt to block this channel is wrong and against international treaties on satellite communication. Whoever is attempting the blocking should stop it now.

Peter Horrocks is the director of BBC World Service.