* HSI +0.7 pct, H-shares +1.4 pct, CSI300 +0.6 pct
* Markets lifted after China flash PMI at 5-mth high
* PetroChina hits 6-month high after China-Russia gas deal
* China CNR dips below offering price in HK debut (Updates to midday)
By Grace Li
HONG KONG, May 22 (Reuters) - Hong Kong and China shares rose on Thursday helped by a preliminary private survey that suggested China's factory sector turned in its best performance in five months in May.
China's gas-related stocks were also buoyed by a long-awaited gas deal between China and Russia, expected to help stabilise gas supply and prices on the mainland.
By midday, the Hang Seng Index was up 0.7 percent at 23,005.27 points, hitting its highest since April 15. The China Enterprises Index of the top Chinese listings in Hong Kong jumped 1.4 percent.
The CSI300 gained 0.6 percent, while the Shanghai Composite Index was up 0.4 percent at 2,033.25 points.
Mainland shares bounced back to positive territory after the HSBC/Markit flash Purchasing Managers' Index (PMI) ticked up to a five-month high of 49.7 in May, from April's final reading of 48.1. But it remained under the 50-point level that demarcates expansion from contraction.
"The data is better than the market had expected," said Zhang Qi, a Shanghai-based analyst with Haitong Securities. "But whether the upward trend can continue depends on whether capital would constantly go to some blue chips."
PetroChina rose 1.1 percent in Hong Kong to its highest since November, after its parent firm, China National Petroleum Corp, signed a $400 billion gas supply deal with Russia's Gazprom late on Wednesday.
The whole gas sector was boosted by the news, with Changchun Gas Co Ltd surging the maximum allowed 10 percent in Shanghai and Shenzhen Gas Corp Ltd jumping 6.1 percent.
Leading the gains in the onshore Chinese markets were also property developers, shrugging off a downgrade by Moody's on Wednesday to negative from stable.
China Fortune Land Co Ltd rebounded 7.1 percent in Shanghai from its two-month low on Tuesday, while China Vanke gained 1.8 percent in Shenzhen.
The improving mood, however, failed to lift the Hong Kong debut of China CNR Corp Ltd , the world's largest train maker by sales. The company's shares fell to HK$5.1, below the HK$5.17 offering price, itself at the lower end of the marketed HK$5.00-HK$6.20 range.
In Hong Kong, Li & Fung rose 2.8 percent in their best day in 9 weeks. The global exporter said the Hong Kong stock exchange would review its application for a separate listing of its global brands business, of which its shareholders will receive one share of the spin-off unit for every share they own in Li & Fung.
Reporting by Grace Li; Editing by Jacqueline Wong