Foreign central banks' overall holdings of U.S. marketable securities at the Federal Reserve fe ll i n the latest week, data from the U.S. central bank showed on Thursday.

The Fed said its holdings of U.S. securities kept for overseas central banks fell $ 9 billion i n the week ended October 3, to stand at $3 . 6 tr illion.

The breakdown of custody holdings showed overseas central banks' holdings of Treasury debt f ell by $ 1 0.3 billion t o stand at $2 . 9 tr illion.

Foreign institutions' holdings of securities issued or guaranteed by the biggest U.S. mortgage financing agencies, including Fannie Mae and Freddie Mac , ro se by $1. 3 bil lion to stand at $70 5 bil lion.

Overseas central banks, particularly those in Asia, have been huge buyers of U.S. debt in recent years and own more than a quarter of marketable Treasuries. China and Japan are the biggest two foreign holders of Treasuries.

The full Fed report can be found on: http://www.federalreserve.gov/releases/h41/ (Reporting by Daniel Bases; Editing by Chizu Nomiyama)