Russia has sent a set of mobile radar jammers to Iran and is negotiating future deliveries that Moscow believes do not contravene the current UN sanction regime on the Islamic state, an official said Tuesday.

The Avtobaza truck-mounted jammers are a part of a broader line of arms that Russia hopes to sell Iran despite concerns over Tehran's nuclear programme, the deputy head of the military and technical cooperation agency said.

"This is a defensive system," the agency's deputy director Konstantin Biryulin was quoted as saying by the state RIA Novosti news agency.

"We are not talking about jets, submarines or even S-300 (missile) systems. We are talking about providing security for the Iranian state."

"We are in constant talks with Iran over that country's purchases of military technology that does not fall under UN sanctions," he was quoted as saying.

The arms delivery was disclosed the same day as one Western diplomat said that Russia and China were both urging the UN atomic agency to soften or even hold back a report detailing Iran's suspected efforts to develop nuclear weapons.

Russia had strongly defended its close trading partner until agreeing in September 2010 to cancel a planned sale of S-300 missile systems and supporting stronger sanctions against Tehran.

But limited arms shipments have continued and Iran last month finally put a Russian-made nuclear power plant on stream after several years of delays in Bushehr.

Biryulin did not disclose when the radar systems were delivered or how many units were sold.