* SSEC -0.1 pct, CSI300 -0.3 pct, HSI -0.3 pct
* Stability in China stocks "temporary" - investor
* PICC shares hit near 2-mth high after China IPO plan
SHANGHAI, May 17 (Reuters) - China stocks fell slightly on Wednesday morning following a four-day rising run as concerns over tighter regulation and economic growth capped a rebound triggered by generous official help.
The blue-chip CSI300 index fell 0.3 percent, to 3,417.52 points by the lunch break, while the Shanghai Composite Index lost 0.1 percent, to 3,109.71 points.
Chinese stocks had declined for five weeks in a row amid concerns that Beijing's stepped-up efforts to reduce leverage in the financial system would trigger liquidity stress and damage the economy.
But the market rebounded in recent sessions after Beijing moved to ease investor concerns through generous cash injections in the interbank market and market-friendly comments.
"After the panic selling triggered by tighter regulations, the market is pausing for breath," said Wu Kan, head of equity trading at Shanshan Finance.
"But the stability could temporary. Future direction depends on the pace of tightening and economic conditions."
Most sectors fell on Wednesday morning, with consumer and healthcare stocks among the worst performers.
Small-cap stocks rebounded, though, with the start-up ChiNext board up 0.7 percent.
Hong Kong stocks, which have so far been immune from China's deleveraging campaign, hovered near 21-month highs.
The Hang Seng index dropped 0.3 percent, to 25,268.11 points, while the Hong Kong China Enterprises Index lost 0.6 percent, to 10,370.06.
Shares of the People's Insurance Group Of China hit a near two-month high after it unveiled plans to list in Shanghai.
But shares of Shanghai Fosun Pharmaceutical Group Co Ltd slumped more than 6 percent after the drugmaker announced plans to offer additional shares at a discount to the market price.
(Reporting by Samuel Shen and John Ruwitch; Editing by Eric Meijer)