* SSEC -2.0 pct; CSI300 -2.4 pct; HSI -1.1 pct
* Insurers pull back from stock markets
* China should set 2017 GDP growth at 6.5 percent- think tank
SHANGHAI, Dec 12 (Reuters) - China stocks slumped to one-month lows on Monday morning, as blue-chips were bruised by a fresh regulatory move to rein in insurers' aggressive share purchases and profit-taking as the year-end approaches.
If the losses at midday aren't pared in the afternoon, the main indexes will have their biggest one-day losses since mid-June.
The downbeat mood spread to Hong Kong, where investors are already cautious ahead of a likely U.S. rate hike this week. Hong Kong's main index opened higher but ended the morning session in negative territory.
The blue-chip CSI300 index fell 2.3 percent, to 3,410.94 points at the end of the morning, and the Shanghai Composite Index lost 2.0 percent, to 3,167.37 points.
The benchmark Hang Seng index dropped 1.1 percent, to 22,503.03 points, while the Hong Kong China Enterprises Index lost 1.4 percent, to 9,732.39 points.
China's insurance regulator, which recently said it would curb "barbaric" acquisitions by insurers, late on Friday said it had suspended Evergrande Life, the insurance arm of China Evergrande Group, from conducting stock market investment.
Also late on Friday, Foresea Life Insurance, a unit of Baoneng, said that it would not further boost stakes in Gree Electric Appliances Inc of Zhuhai. Gree shares, which had surged by Forsea Life's aggressive stake-building, lost 4.7 percent on Monday morning.
Other companies favoured by insurers, including China Vanke Co Ltd, China State Construction Engineering Corp Ltd and Poly Real Estate Group Co Ltd, also saw their shares tumble.
Zhang Qi, analyst at Haitong Securities in Shanghai, said sentiment was soured by regulators' measures as well as profit-taking as the year-end nears.
Another factor denting sentiment may have been a suggestion by an official think-tank for China to set a growth target of 6.5 percent for 2017. China has been on track for 6.7 percent this year.
Nearly all sectors lost ground in China and Hong Kong.
Energy suffered the least in China and Hong Kong, thanks to an oil price surge in the morning after OPEC and other producers reached their first deal since 2001 over the weekend to jointly reduce output.
Reporting by Jackie Cai and John Ruwitch; Editing by Richard Borsuk