BEIJING/SHANGHAI, May 19 (Reuters) - China shares slipped on Wednesday after three straight sessions of gains, dragged down by energy firms and banks, while digital currency-related stocks also fell after Beijing banned financial and payment companies from the cryptocurrency business. ** By the midday break, the Shanghai Composite index was down 0.41% to 3,514.38, while the blue-chip CSI300 index was lower 0.11%. ** The energy sector sub-index fell 1.63%, the banking sector was down 1.39%, and the real estate index dropped 1.23%. ** Investors are betting on the increasing momentum of A shares and searching for opportunities in consumer blue-chips and new energy vehicles firms, said Yang Delong, an investment manager at First Seafront Fund Management Co. ** Trading in the mainland market is volatile, Yang said, citing relative low valuations for A-shares and Hong Kong stocks amid surging global equities. ** China has banned financial institutions and payment companies from providing services related to cryptocurrency transactions, and warned investors against speculative crypto trading. ** The smaller Shenzhen index rose 0.14%, the start-up board ChiNext Composite index was higher by 0.88% and Shanghai’s tech-focused STAR50 index climbed 0.58%. ** Hong Kong markets were closed for a holiday. ** Around the region, MSCI’s Asia ex-Japan stock index was weaker by 0.33%, while Japan’s Nikkei index was down 1.52%. (Reporting by Cheng Leng in Beijing, Luoyan Liu and Andrew Galbraith in Shanghai; Editing by Subhranshu Sahu) Our Standards: The Thomson Reuters Trust Principles.