* CSI300 +0.7 pct; SSEC +0.4 pct; HSI -0.3 pct
* Banks only slightly affected by investigations
* 30 SOEs expected to post losses in 2015 - paper
By Sue-Lin Wong
SHANGHAI, Feb 3 (Reuters) - China stocks rebounded on Tuesday after five straight days of losses, helped by energy and financials, after sentiment took a hit from worries over margin trading curbs and new listings.
"The market is weak as blue chips recover from yesterday's losses," said Du Changchun, an analyst at Northeast Securities in Shanghai.
China's stocks regulator has stepped up investigations on brokerage margin financing that has been blamed for speculative activity and investors are also concerned about official probes on firms for corruption.
The CSI300 index rose 0.7 percent, to 3,376.55 points at the end of the morning session, while the Shanghai Composite Index gained 0.4 percent, to 3,141.40 points.
Bank of Beijing slipped 0.2 percent after the bank said its director was being investigated for "disciplinary violations".
But China's Minsheng Bank was up 0.6 percent in Shanghai and 0.4 percent in Hong Kong, recovering from sharp falls the previous day after its president resigned over the weekend. His resignation came after media reports said he was being investigated by China's anti-corruption watchdog.
The energy sub-index rose 1.0 percent and the bank sub-index was up 0.4 percent.
"The news of Minsheng and Bank of Beijing hasn't had a huge impact on the banking sub-index because I don't think investors are worried about banks' fundamentals," said Du.
ChiNext, Shenzhen's NASDAQ-like index, jumped 2.7 percent as profit-taking from blue chips flowed into small and mid caps, analysts said.
Of the 145 listed state-owned enterprises (SOEs) in China, 30 are expected to post losses in 2015, according to a report in the Shanghai Securities News on Tuesday.
In Hong Kong, the Hang Seng index dropped 0.3 percent, to 24,406.92 points.
The Hong Kong China Enterprises Index lost 0.2 percent, to 11,557.72.
Lenovo, the world's leading PC maker, jumped to 6.3 percent after the company said its third-quarter revenue rose 31 percent to $14.1 billion after its acquisition of Motorola.
The index measuring price differences between dual-listed companies in Shanghai and Hong Kong stood at 123.54.
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.
Total volume of A shares traded in Shanghai was 12.29 billion shares, while Shenzhen volume was 7.75 billion shares.
Total trading volume of companies included in the HSI index was 0.7 billion shares.
Additional reporting by the Shanghai Newsroom; Editing by Jacqueline Wong