* CSI300 -0.3 pct; SSEC -0.2 pct; HSI -1.6 pct
* China market rebound has priced in much of policy hopes-investor
* Hong Kong energy shares slump on lower oil prices
SHANGHAI, Feb 24 (Reuters) - China stocks were easier on Wednesday morning, with sentiment eroded by a slump in Shenzhen's start-up board where the market will come under greater regulatory scrutiny.
Hong Kong shares also sagged, tracking global markets, and were dragged down by the energy sector after oil prices pulled back.
The blue-chip CSI300 index fell 0.3 percent, to 3,079.12 points by lunch break, while the Shanghai Composite Index lost 0.2 percent, to 2,897.25 points.
The market has rebounded roughly 10 percent over the past month, propelled by a bounce in global markets, signs of yuan stabilisation, and policy expectations ahead of a meeting by China's legislature that starts March 5.
However, Zhang Chen, strategist at Shanghai Maoshuo Asset Management Co, expected the rebound to lose some steam, with its sustainability hinging largely upon whether policies announced during the National People's Congress (NPC) gathering could exceed expectations.
"The market will become more volatile as much of the policy expectation has been priced in, so if policies fail to excite investors, the market may fall again," Zhang said.
Beijing has already unveiled a series of measures this year to tackle overcapacity and excessive inventory issues in industries ranging from coal, steel, and property.
Chinese president Xi Jinping urged officials at all levels to implement reforms and address lingering problems, the official Xinhua news agency reported on Wednesday.
Most sectors fell, but infrastructure and transportation stocks rose, while resource shares kept their upward momentum.
Shenzhen's ChiNext slumped 1.6 percent, after a media report citing sources that said China's new securities chief vowed to step up the fight against malpractices. Analysts said small stocks were more vulnerable to the government's clampdown.
In Hong Kong, the Hang Seng index dropped 1.6 percent, to 19,103.70 points, while the Hong Kong China Enterprises Index lost 2.0 percent, to 8,006.95.
Energy shares tumbled as oil prices skidded after Saudi Arabia effectively ruled out production cuts by major producers anytime soon.
Reporting by Samuel Shen and Pete Sweeney; Editing by Jacqueline Wong