Regional and Hong Kong markets retreated at the opening of trading on Friday Japan's Nikkei share average sank on Friday amid overnight losses on Wall Street for tech stocks as concerns over sky-high valuations mounted again.

The benchmark Hang Seng Index fell 412 points, or 1.52 percent, to open at 26,660.

On the mainland, the benchmark Shanghai Composite Index was down 0.56 percent at 4,007 while the Shenzhen Component Index was 1.14 percent lower at 13,323 and the ChiNext Index, tracking China's Nasdaq-style board of growth enterprises, was down 1.74 percent at 3,145.

The S&P/ASX 200 index opened at 8,637, down 116.2 points, or 1.33 percent.

In Tokyo, the 225-issue Nikkei Stock Average opened at 50,767 points, down 514 points, or 1 percent.

The Nikkei fell as much as 2 percent early in the session but recovered slightly to trade 1.3 percent lower at 50,630 once the initial round of selling subsided.

The broader Topix lost 0.7 percent to 3,358.

The Korea Composite Stock Price Index opened at 4,061 points, down 108 points, or 2.61 percent. (Reuters/Xinhua)