'A contract to deliver SU-30MK2 (jets) was signed by (state arms export monopoly) Rosoboronexport at the start of the year,' Interfax news agency quoted a defence industry source as saying.

Vedomosti business daily, citing two defence industry sources, said deliveries of the 12 supersonic jets would begin next year. Rosoboronexport refused to comment on the report.

Experts polled by Vedomosti and Interfax estimated the contract would be worth between US$500 million and $600 million.

The Su-30, known as 'Flanker-C' to NATO, is a more formidable version of the Su-27. It made its first flight in the days of the Soviet Union but was introduced to service in post-communist Russia in 1996.

Vedomosti reported in April that Vietnam was in talks with Rosoboronexport to deliver six Project 636 Kilo-class diesel-powered submarines in a deal estimated by the business daily at US$1.8 billion.

If that deal is secured, Vietnam would become one of Russia's top-five arms sales customers, Vedomosti reported. -- REUTERS