China's holdings of US Treasury securities fell 9.3 percent from September to December to $1.1529 trillion -- with most of the fall coming apparently in the final month of the quarter, according to the revised Treasury data.

In addition, US Treasury bonds held by Chinese territory Hong Kong totalled $121.7 billion in December, up $10.1 billion from September.

The new data showed Japan closing in on China's ranking as the top foreign investor in US debt.

Japan's Treasuries holdings rose 7.5 percent in the quarter to $1.0582 trillion.

The drop in China's share paralleled a sharp fall in China's overall foreign exchange reserves late last year.

In January, Beijing reported its total foreign exchange reserves, including US debt, fell to $3.18 trillion at the end of December from a peak of $3.27 trillion in October.

The fall came as its trade surplus began to narrow and as capital moved out of the country amid expectations that the yuan's appreciation against the dollar would ease.