Western powers on Wednesday condemned what they called Iranian efforts to arm Syria's government, which is battling a mounting opposition uprising.
A number of violations of UN sanctions against Iran reported to UN experts in recent months have involved transfers of arms from Iran to Syria, diplomats said. The cases are being investigated.
"The extent confirms the existence of a deliberate and continued policy of illicit transfers of arms and related material between Iran and Syria," Martin Briens, France's deputy UN ambassador, told a UN Security Council meeting.
Similar concerns were raised by the United States and Britain at the meeting of the committee monitoring four rounds of UN sanctions ordered against Iran over its nuclear program.
"We are alarmed that a majority of the violations reported to the committee involved illicit transfers of arms and related material from Iran to Syria, where the Assad regime is using them to violently repress the Syrian people," said the deputy US ambassador Rosemary DiCarlo.
The United States called for "targeted sanctions on individuals and entities found to be involved in sanctions violations."
Britain's UN envoy, Mark Lyall Grant, said there was "emerging evidence of systematic Iranian activity to provide weapons illegally to the Syrian government -- weapons which, as we speak, are being used to violently suppress the people of Syria."
The French envoy said at least one case of suspected arms transfers had been reported to the sanctions committee in the past three months.
Diplomats said a number had been reported since the uprising against President Bashar al-Assad started one year ago. The sanctions committee inquiries are normally kept confidential.
The United States said last week it is concerned about Iranian cargo flights over Iraq to Syria. The US State Department said it had warned Iraq they might contain arms that could be used by Damascus to crush protests.
The United States imposed sanctions on Iran's intelligence ministry in February, partly because of allegations that it had supported Syria's crackdown on dissent.
Two Iranian warships which docked in the Syrian port of Tartous in February also drew international attention.
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