Hong Kong's benchmark stock index closed at its lowest level in nearly 3-1/2 years on Friday, pounded by tumbling mainland stocks and a drop of the Hong Kong dollar against the U.S. dollar.

The Hang Seng index fell 1.5 percent, to 19,520.77, the lowest close since September 2012. The China Enterprises Index lost 2.6 percent, to 8,236.28 points.

For the week, Hang Seng was down 4.6 percent.

Total trading volume of companies included in the HSI index was 2.0 billion shares.