* SSEC flat, CSI300 flat, HSI +0.3 pct
* Southbound quota of Shanghai-HK stock connect utilised 17.4 pct as of noon
SHANGHAI, Sept 6 (Reuters) - China stocks were flat on Tuesday morning, while Hong Kong's market rose for the fourth day led by investors continuing to search for higher yield as authorities in the mainland persisted with efforts to reduce leverage in the financial system.
As of noon, the benchmark Hang Seng index added 0.3 percent, to 23,726.09 points. The Hong Kong China Enterprises Index gained 0.7 percent, to 9,901.77.
The mood in the Hong Kong market has been buoyed by a flood of capital pouring in from the mainland since last week, as investors there actively hunt for yields in a low-interest rate environment. Others are also seeking to front-run a cross-border investment link between Shenzhen and Hong Kong that is expected to be launched in November.
Last week, Chinese investors spent 17.7 billion yuan ($2.65 billion) buying Hong Kong stocks under the Shanghai-Hong Kong Stock Connect, the biggest weekly inflows since last April.
"But investors have become cautious now," Sam Chi Yung, a senior strategist at South China Financial Holdings in Hong Kong wrote in a note on Tuesday, suggesting the Hang Seng index may take a breathe after it hit a series of one-year highs in recent days.
Some analysts said Hong Kong market has outperformed its mainland counterpart as stocks listed in Hong Kong are relatively "cheap".
"In China, money is moving into properties, rather than stocks, as regulators are reducing leverage in financial markets. It may take a while before Chinese stocks resume its uptrend again," said Yang Hai, analyst at Kaiyuan Securities Co. in Xi'an.
China central bank in August injected cash into money markets through 14-day reverse repo agreements for the first time since February in a sign policymakers were worried rising leverage could stoke bubbles in the bond market.
The CSI300 index was flat at 3,321.17 points at the end of the morning session, while the Shanghai Composite Index was also flat at 3,072.86 points.
The index measuring price differences between dual-listed companies in Shanghai and Hong Kong stood at 120.70.
A value above 100 indicates Shanghai shares are pricing at a premium to shares in the same company trading in Hong Kong, and vice versa.
The southbound quota for the Shanghai-Hong Kong Stock Connect, currently set at 10.5 billion yuan, utilised 1.83 billion yuan, or 17.4 percent in morning trade.
Reporting By Winni Zhou, Samuel Shen and Nathaniel Taplin; Editing by Shri Navaratnam