BEIJING, Dec. 16 -- Chinese banks purchased forex worth 164.7 billion U.S. dollars last month while selling 128.1 billion U.S. dollars, a surplus of 36.6 billion U.S. dollars.

It marked the fourth month of surplus since August, after a deficit in June and July, according to the State Administration of Foreign Exchange.

Analysts attributed the surplus to growth of the economy, appreciation of Renminbi and delay of the U.S. Federal Reserve's tapering off of quantitative easing (QE3).

Foreign exchange transactions are a major cause of fluctuation in China's foreign exchange reserves, and the November surplus indicates a slowing outflow of foreign capital.

In the January-November period, forex purchases stood at 1.7 trillion U.S. dollars, with sales of 1.46 trillion U.S. dollars, a surplus of 239.2 billion U.S. dollars.