(Corrects number of firm plane orders in bullet point, lead and 6th paragraph)

Russian-Italian planemaker Superjet has sealed a $900 million deal to sell 30 aircraft to a Bermuda-based leasing firm, marking its second significant firm order in three days.

The Superjet 100 will be the first passenger plane built by Russia since the fall of the Soviet Union, and will attempt to challenge market leaders Boeing and Airbus in the regional carrier sector.

The joint venture Superjet International, majority owned by Russia's Sukhoi , said on Thursday it had agreed to sell the Superjet 100 planes to new group Pearl and would begin deliveries in 2011.

This agreement with an international leasing company is proof of the quality of this aircraft and further enhances our position in the market, Superjet Chief Executive Alessandro Franzoni said in a statement.

The deal also includes an option to deliver 15 further aircraft to the same company.

Superjet is 25 percent owned by Italy's Finmeccanica . The company announced 30 other firm orders earlier in the week, part of a glut of commercial plane orders that have dominated this year's Farnborough Airshow.

In a separate deal, Gazpromavia -- the airline owned by Russian state gas monopoly Gazprom -- said it had signed a letter of intent to buy 10 Superjet 100s, although it did not give a value.

And Russia's OAK -- the owner of Sukhoi -- also said it had signed a deal to sell 50 MC-21 passenger planes to Malaysian firm Crecom.

(Reporting by Rhys Jones and Gleb Stolyarov, Writing by John Bowker, Editing by Ben Berkowitz)