It is the highest amount pumped into the market since February 2010, when the central bank injected RON6.42 billion at a 7% annual yield.
The central bank bought treasuries from 10 lenders and will sell them back November 28.
Dealers expected the central bank would try to boost liquidity, following repeated interventions in the money market last week to support a weakening leu, which drove rates higher.
On the money market Monday morning, overnight rates fell to 5.7%-6.2% a year, from 7.1%-7.6% a year Friday. (EUR1=RON4.3608)