The unprecedented move by the International Telecommunication Union (ITU) adds to pressure on Tehran as world powers consider a new round of U.N. sanctions over Iran's nuclear programme and it faces simmering social unrest.
Iranian authorities have been jamming foreign satellite broadcasts into their territory since late last year, with broadcasters such as the BBC and Deutsche Welle affected. Access to the Internet for Iranian citizens has also been affected.
In a statement, ITU's radio regulations board said interference coming from Iran was harming signals from satellite networks run by Eutelsat, a French satellite operator.
Iran should find the source of the interference — which affects both radio and television signals — and "eliminate it as a matter of highest priority".
"In this case there is evidence that there is a deliberate attempt to block the satellite transmissions and so they are saying this should be stopped. This is prohibited under the regulations," ITU spokesman Sanjay Acharya told a news briefing.
"Iran has not admitted it is sending out these signals that are interfering with Eutelsat. They have said they will investigate," he added.
PRESIDENTIAL ELECTION
Iranian authorities have been clamping down on reformists since last year's June disputed presidential election returned hardliner Mahmoud Ahmadinejad to power, sparking protests and clashes. Iran has blamed other nations for stoking unrest.
On Monday, European Union foreign ministers also urged Iran to stop jamming transmissions and said they were prepared to take action to put an end to the interference.
France raised the issue at the closed-door talks of ITU's 12-member experts board and provided evidence that there were signals from Iran which interfered with Eutelsat, ITU said.
"This is the first time that the radio regulations board has had to take this step," Acharya told Reuters, noting that the case involved a "deliberate attempt to block a signal".
Previous disputes brought to the ITU involved satellites from different European states interfering with each other, or Cuba complaining about U.S.-based terrestrial operators sending signals into the communist island, he said.
The board has no policing powers to enforce its decision, but its appeal is expected to put pressure on Iran, which is one of 191 ITU member states, to stop the practice, Acharya said.
"We will put as much pressure as possible and this is the beginning of that," he said.
ITU's ruling Council could take up the issue at its annual meeting being held in Geneva from April 13-22, but bilateral efforts were expected to continue in the meantime, he said.
"Iran is a member of the ITU and has to adhere to treaties that have been signed on radio regulations," Acharya said. "No one is allowed to block signals, that is clear." (Editing by Jonathan Lynn)
