China's foreign exchange watchdog said Wednesday that Chinese banks' foreign exchange surplus from bank-to-client transactions reached 37.8 billion U.S. dollars in August.

In August, institutional and individual clients sold 144.4 billion U.S. dollars in foreign currencies to banks while purchasing 106.5 billion U.S. dollars, the State Administration of Foreign Exchange (SAFE) said in an online statement.

From January to August, more foreign currencies were sold than purchased through Chinese banks, resulting in 354.8 billion U.S. dollars of foreign exchange surplus during the period, the statement said.

Foreign exchange surpluses, which make up part of China's foreign exchange reserves along with current account surpluses and foreign direct investment inflow, do not include banks' own foreign exchange transactions or interbank transactions, according to SAFE.

Last year, foreign exchange surpluses created through Chinese banks' transactions with domestic clients increased 51 percent year-on-year to reach 397.7 billion U.S. dollars, SAFE data showed.