TEHRAN, May 16 (Reuters) - Russian Deputy Prime Minister Alexander Novak, in charge of energy diplomacy, started a visit to Iran on Tuesday and stressed the benefits of more cooperation in the oil and gas sectors, Moscow said.

Russia and Iran, both under Western sanctions, are forging closer ties in order to support their economies and to undermine Western sanctions which they both cast as unjustified.

Novak met Iranian Oil Minister Javad Owji and also visited a number of oil and gas equipment manufacturers and discussed prospects for working together in the fuel, energy and transport sectors, the Russian government said in a statement.

"The oil and gas industry is a backbone for the economies of our countries. Strengthening bilateral cooperation in this area will undoubtedly increase the economic sustainability of Russia and Iran," it quoted Novak as saying.

The two sides also discussed cooperation in the field of electrical and nuclear energy as well as renewable energy sources, the statement added, but gave no details.

Russia started fuel exports to Iran by rail this year for the first time after traditional buyers shunned trade with Moscow, industry sources and exports data revealed in April.