MOSCOW, Sept 14 (Reuters) - The share of Russia’s OFZ treasury bonds held by non-residents increased in August by 1.0 percentage point to 20.9%, the central bank said in its report on Tuesday. The non-residents bought 24.5% of OFZs that the finance ministry sold at weekly auctions in August, the central bank said. Major Russian banks remain the main buyers of the rouble-denominated OFZ bonds which Russia uses to plug holes in its budget. (Reporting by Elena Fabrichnaya; writing by Polina Devitt; editing by Chris Reese)