BEIJING, Oct. 23-- China's appetite for foreign currency increased in September, leading to a widening deficit in foreign exchange transactions among banks, the country's top foreign exchange regulator said Thursday.

Chinese institutions and individuals bought 179.3 billion U.S. dollars in foreign currency and sold 163 billion U.S. dollars in exchange for 1.1 trillion yuan in September, according to data from the State Administration of Foreign Exchange (SAFE).

As a result, the banks' forex transaction deficit more than doubled to 16.3 billion U.S. dollars from that in August, when Chinese banks posted their first monthly net foreign exchange purchase in 13 months.

In the first nine months, Chinese sold 1.43 trillion U.S. dollars of foreign currency in exchange for 8.78 trillion yuan while buying 1.25 trillion U.S. dollars in foreign currency, resulting in net foreign exchange sales of 172.3 billion U.S. dollars.

The fluctuation in forex transactions contributed to changes in China's foreign reserves.