SHANGHAI, May 30 (Reuters) - China and Hong Kong stocks fell on Tuesday as investor sentiment remained bearish ahead of China's May manufacturing data.

** China's blue-chip CSI300 Index dropped 0.8% by the lunch break, while the Shanghai Composite Index lost 0.7%.

** Hong Kong's benchmark Hang Seng Index and the China Enterprises Index were both down 1.0%.

** China's factory activity likely contracted further in May, a Reuters poll showed on Monday, adding to pressures facing the world's second-biggest economy amid an uneven economic recovery from the COVID-19 pandemic. The official manufacturing Purchasing Managers' Index (PMI) will be released on Wednesday.

** "Sentiment around China continues to be bearish ahead of May's manufacturing PMI due on Wednesday," UBS analysts wrote in a note.

** Meanwhile, tensions between the world's two largest economies continued. China has declined a request by the United States for a meeting between their defense chiefs at an annual security forum in Singapore this weekend, media reported on Monday, a new sign of strain between the powers.

** Shares of some artificial intelligence companies soared on the brain-computer interface concept, with Innovative Medical Management Co Ltd and Jiangsu Apon Medical Technology Co Ltd surging 10.0% and 20.0%, respectively.

** Stocks of state-owned enterprises (SOEs) regained popularity among investors. CRRC Corp Ltd, the rolling stock manufacturer giant, rose as much as 10%.

** Tech stocks traded in Hong Kong lost 0.7%, with Meituan and Tencent down 2.4% and 1.0%, respectively, dragging the Hang Seng Index down. (Reporting by Shanghai Newsroom; Editing by Sohini Goswami)