* HSI -0.9 pct, H-shares -1.4 pct, CSI300 -1 pct
* Aluminium producers outperform on rise in prices
* Coal producers down as Beijing orders curbs on oversupply
* ZTE hits 8-1/2-month high after strong H1 earnings (Updates to midday)
By Grace Li
HONG KONG, Aug 21 (Reuters) - Hong Kong and China shares weakened on Thursday after a preliminary private survey showed growth in China's vast factory sector slowed to a three-month low in August, reinforcing concerns about increasing softness in the economy.
The HSBC/Markit Flash China Manufacturing Purchasing Managers' Index (PMI) fell to 50.3 from July's 18-month high of 51.7, missing a Reuters forecast of 51.5.
By midday, the CSI300 of the leading Shanghai and Shenzhen A-share listings lost 1 percent, while the Shanghai Composite Index was down 0.9 percent at 2,220.51 points. Both slipped the most in two weeks.
The Hang Seng Index was off 0.9 percent at 24,927.05 points. The China Enterprises Index of the top Chinese listings in Hong Kong fell 1.4 percent. If losses hold, these would be their worst daily losses in six weeks.
Mark To, head of research at Hong Kong's Wing Fung Financial Group, said profit-taking was obvious on Thursday and the PMI survey was the trigger.
"Some consolidation is still quite healthy, because most of the people are looking at the Shanghai-Hong Kong connect. That should be a theme we can enjoy even for the coming few months," To said. The scheme, set to be launched in October, will allow Chinese to invest in Hong Kong's H-shares and foreign investors to buy Shanghai's A-shares through brokers located in Hong Kong.
"People may just have some kind of profit-taking and then the other investors who haven't enjoyed the rally and ridden the tide may choose to enter the market very soon."
PetroChina and China Petroleum & Chemical Corp were top index drags in Shanghai, down 0.6 and 1.3 percent, respectively.
Coal stocks were broadly weaker as China's top economic planner ordered local governments to step up supervision to regulate coal output and to severely punish miners that produce beyond their approved capacity.
China Shenhua Energy , the mainland's biggest coal producer, shed 2.2 percent in Shanghai and 1.9 percent in Hong Kong.
Aluminium producers were key outperformers as the metal's price hit a 1-1/2-year high overnight. Henan Mingtai Al.Industrial rose 1.9 percent and Yunnan Aluminium 3 percent.
Earnings remained the focus for many other stocks.
ZTE Corp jumped more than 5 percent to its highest since early December in early trade, after the Chinese telecom equipment maker posted a record first-half net profit thanks to improving margins and revenue from new contracts to build China's next-generation telecom network. It finished the morning session up 2.5 percent.
China Resources Power leapt 3.9 percent to a 15-month high. JP Morgan lifted the shares' target price to HK$28.5 from HK$26.6 as the company's interim results beat expectations. (Editing by Jacqueline Wong)