* HSI flat, H-shares -0.5, CSI300 -0.3 pct
* 11 Chinese firms to launch IPOs, could dilute valuations
* Earnings performance, strong global market boost HK
* New stock account openings at 4-mth high
By Chen Yixin and Pete Sweeney
SHANGHAI, Aug 20 (Reuters) - China's stock indexes fell slightly by midday on Wednesday, on worries that upcoming initial public offerings (IPOs) will tax market liquidity even as investors look to take profits from a rise in large-cap shares.
Hong Kong stocks, however, found some support on positive earnings results from index majors and strong performance in offshore equity markets.
By midday, the CSI300 index of leading Shanghai and Shenzhen A-share listings was down 0.3 percent. The Shanghai Composite fell 0.1 percent to 2,242.96 points.
In Hong Kong, the HSI index edged up 0.01 percent to 25,124.73 points, with the China share sub-component 0.5 percent lower at 11,040.16 points.
Late on Tuesday, the Chinese Securities Regulatory Commission (CSRC) announced that 11 Chinese companies would launch IPOs, with subscriptions starting at the end of August.
"This information has some impact on liquidity in today's market, as investors are expected to set aside money to purchase new shares," said Du Changchun, an analyst from Northeast Securities in Shanghai.
He said that profit-taking seen in some index heavyweight shares, as well as a sell-off in media shares from the ChiNext board after a three-day rally, also dragged on the market.
Most analysts hold positive views on the domestic market. Some said that despite momentum weakening in recent days, the market was still on an upward trend. One analyst noted the market had been in bullish mode since the end of July.
The number of stock accounts opened at mainland brokerages last week broke 150,000, the highest level in four months, the official Shanghai Securities News reported on Wednesday citing a private survey.
The paper also reported that the head of the debt financing department at Haitong Securities Co Ltd was involved in a bond market anti-corruption probe, but the market appeared to shrug off the news, with shares of the securities firm easing only 0.5 percent in line with the broader market.
Several major-listed companies and banks in Hong Kong posted stronger than expected first-half earnings late on Tuesday. They included Brilliance China Auto, up 5.1 percent, which lent support to the Hong Kong market hovering around six-year highs, analysts said.
"Companies announcing strong results -- such as Brilliance China -- have raised interest in related stocks such as Dongfeng," said Ben Kwong, head of research and director of KGI Asia.
Dongfeng Motor Group was up more than 2 percent.
Additional reporting Shanghai Newsroom; Editing by Jacqueline Wong