U.S. Fed buys $7.8 billion of mortgage bonds, sells none

from Nov. 30 to Dec. 6, compared with $3.447 billion purchased the previous week, the New York Federal Reserve Bank said on Thursday.

In a move to help the housing market begun in October 2011, the U.S. central bank has been using funds from principal payments

on the agency debt and agency mortgage-backed securities, or MBS, it holds to reinvest in agency MBS.

The New York Fed said on its website the Fed sold no mortgage securities guaranteed by Fannie Mae ,

Freddie Mac or the Government National Mortgage Association, or Ginnie Mae,

in the latest week. It sold none the prior week.