* SSEC -1.6 pct; CSI300 -1.5 pct; HSI -1.9 pct
* Materials companies lead drop in cyclical A-shares
* China cyber authority probe hits shares of Tencent
SHANGHAI, Aug 11 (Reuters) - China stocks fell sharply early Friday as fears over escalating tensions between North Korea and the United States spread to mainland investors, and as cyclical shares continued to retreat after recent gains.
The CSI300 index fell 1.5 percent, to 3,659.34 points at the end of the morning session, while the Shanghai Composite Index lost 1.6 percent, to 3,209.66 points.
The Hang Seng index tumbled 1.9 percent, to 26,926.38 points. The Hong Kong China Enterprises Index lost 2.0 percent, to 10,566.39.
"Tensions between the U.S. and North Korea have been affecting markets around the world, and they are now affecting markets in China," said an analyst at Huarong Securities in Beijing.
"We are also seeing a continued correction in cyclical shares," he said.
China CSI300 stock index futures for August fell 1.4 percent, to 3,650.2, 9.14 points below the current value of the underlying index.
Materials firms continued their downward course, with the CSI's materials sub-index dropping 4.2 percent. Xiamen Tungsten fell 8.6 percent, and Jiangxi Copper lost 8.0 percent as prices of some metals in Shanghai also felt the pressure of rising North Korea-United States tensions.
Hong Kong shares were hit by Tencent Holdings Ltd, which fell 4.0 percent. The stock, which recently hit record highs, came under pressure after China's top cyber authority said on it is investigating popular internet platforms including Tencent's WeChat, Weibo Corp and Baidu Inc's forum site Tieba.
The index measuring price differences between dual-listed companies in Shanghai and Hong Kong stood at 128.87.
A value above 100 indicates Shanghai shares are pricing at a premium to shares in the same company trading in Hong Kong, and vice versa.
Reporting by Andrew Galbraith; Editing by Richard Borsuk