Israel is looking into reports that Russia plans to sell 250 advanced long-range Sukhoi-30 fighter jets to Iran in an unprecedented billion-dollar deal.

According to reports, in addition to the fighter jets, Teheran also plans to purchase a number of aerial fuel tankers that are compatible with the Sukhoi and capable of extending its range by thousands of kilometers. Defense officials said the Sukhoi sale would grant Iran long-range offensive capabilities.

Government officials voiced concern over the reports. They said Russia could be trying to compete with the United States, which announced over the weekend a billion-dollar arms sale to Saudi Arabia and other Gulf states.

Despite Israeli and US opposition, Russia recently supplied Iran with advanced antiaircraft systems used to protect Teheran's nuclear installations. At the time, Moscow said it reserved the right to sell Iran weapons, such as the antiaircraft system, that were of a defensive nature.

The Sukhoi-30 is a two-seat multi-role fighter jet and bomber capable of operating at significant distances from home base and in poor weather conditions. The aircraft enjoys a wide range of combat capabilities and is used for air patrol, air defense, ground attacks, enemy air defense suppression and air-to-air combat.

After years of negotiations, the Indian Air Force in 1996 purchased 40 Sukhoi-30s and in 2000 acquired the license from the company to manufacture an additional 140 aircrafts.