The Federal Reserve bought about $21.6 billion of agency mortgage-backed securities for the week of March 15, up from $18.9 billion a week earlier, the Federal Reserve Bank of New York said.

The central bank sold $3.35 billion in mortgage securities guaranteed by the government-sponsored enterprises this week. The Fed also sold $600 million the previous week.

Since October 2011, the Fed has used funds from principal payments on the agency debt and agency MBS it holds to reinvest in agency MBS, which continues to aid the housing market.