* HSI +0.8 pct, CSI300 +0.9 pct
* Hang Seng hits highest level since 2008
* Solar shares lifted after China halts polysilicon imports
* China Mobile leaps on report of messaging service investment
By Chen Yixin and Pete Sweeney
SHANGHAI, Aug 15 (Reuters) - China's stock indexes rose nearly 1 percent by midday Friday, supported by large-cap shares, while a surge for China Mobile lifted the Hang Seng Index to its highest level since May 2008.
At midday, the CSI300 of leading Shanghai and Shenzhen A-share listings was up 0.9 percent and the Shanghai Composite Index was ahead 0.8 percent at 2223.39 points.
The Hang Seng Index briefly hit a 75-month high when it crossed above 24,988.57 points.
The HSI was propelled by index heavyweight China Mobile , which rose more than 5 percent after official media reported the state-owned telecom giant would increase investment in instant messaging service Fetion.
Analysts saw little room for further index rises given concerns about company results and the Chinese economy. A rally in mainland shares beginning in July, that saw the CSI300 gain more than 10 percent at one point, has flattened out following weak Chinese economic indicators for July.
"Investors are getting cautious after the recent strength in the local market," said Ben Kwong, head of research and director of KGI Asia. "The market may consolidate in the short run waiting for fresh incentives to advance."
For now, investors will focus on major corporate earnings, Kwong said.
Liu Jingde, analyst at Cinda Securities in Beijing, believed mainland indexes have stabilized after a correction in banking shares earlier in the week. He said he expected "mild" share movements in the near future.
Blue-chip shares, including banking and brokerages, were the biggest index supporters on Friday. Almost all banks and brokerages shares rose, with Bank of Ningbo Co climbing 1.3 percent and Guo Yuan Securities Company Limited jumping 6.2 percent.
Polysilicon-related companies enjoyed a boost after China announced that it will halt imports of processed polysilicon on Sept. 1.
Jiangsu Huasheng Tianlong Photoelectric jumped 5.9 percent by midday and Zhejiang Jingong Science & Technology CO. rose 1.6 percent. (Additional reporting by Donny Kwok in HONG KONG; Editing by Richard Borsuk)