The first two aircraft will be delivered in 2008, and the remaining four in 2009.
Ilyushin Finance also signed a similar agreement for six Tu-204 aircraft with Moscow-based airline Airlines-400. The start of deliveries is planned for 2008, and the planes will be leased for 15 years.
An Ilyushin representative said the two contracts are worth about $500 million.
An-148 is designed for passenger, cargo-passenger and cargo transportation flights. It was first presented in Zhukovsky in 2005.
Tu-204, a mid-range airliner seating 210 passengers, was designed as a family of passenger, cargo, mixed planes and convertible variants.
The Rossia company is 100% owned by the state. It presently has a fleet of two Il-62s, four Il-86s, 21 Tu-154Ms, two Tu-154Bs, three Tu-214s, nine Tu-134As, four Yak-40s, five Boeing 737-500 and two Airbus A-319.
Ilyushin Finance deals with financial and operational leasing of Russian-made civil aircraft, funding of export supplies and provides consulting services.
Ilyushin Finance has a 38% stake in Russia's United Aircraft Corporation (UAC).
UAC, which is 90% state owned, consolidates aircraft building companies and state assets, and engages in the manufacture, design and sale of military, civil, transport, and unmanned aircraft in a bid to streamline the Russian aviation industry.
It incorporates commercial and military aircraft makers, such as Sukhoi, Ilyushin, and Tupolev, as well as companies involved in distribution, including Aviaexport.