Russia is working on a series of spyplanes that would be undetectable by air defence systems, the chief of Russia's air force said Wednesday.

"A special role in the air force's future strategy is set for a dramatically new class of spy planes -- high-flying stratosphere aircraft able to monitor a war zone without entering the defended air space," General Alexander Zelin was quoted as saying by the RIA Novosti news agency.

Russia currently relies on the Su-24MR and MIG-25RB intelligence airplanes, Zelin said, adding that the airforce had "a sufficient number of them."

However, modern warfare required a higher level of information gathering which had forced the Russian airforce to dramatically upgrade its intelligence corps, Zelin said.