The Reserve Bank turned a net buyer of dollars in December, the first time in the current fiscal year, as it purchased $607 million of the greenback on a net basis from the spot market, according to the latest data. The central bank bought $837 million and sold $230 million in the spot market during the reporting month. As against this, in December 2017, the RBI was a net buyer of $5.647 billion, after it bought $6.008 billion from the market and sold $361 million.