HONG KONG, May 30 (Reuters) - Hong Kong shares snapped a three-day winning streak on Wednesday, hit by weakness in recent outperformers after media reports damped expectations that Beijing is considering another massive stimulus programme.
The Hang Seng Index closed down 1.92 percent at 18,690.22. The China Enterprises Index of top mainland Chinese listings in Hong Kong ended down 1.7 percent at 9,690.67.
In the mainland, the large cap-focused CSI300 Index slipped 0.32 percent, while the Shanghai Composite Index shed 0.21 percent.
* The Hang Seng Index rolled back this week's gains, slipping below the 50 percent Fibonacci retracement of its rise from the October 2011 low to February 2012 high at about 18,966 points. The benchmark first slipped below this level on May 18, struggling to break above it for longer than a day and bounded by a 500-point range.
* Chinese railway companies, which have surged since Beijing recently announced measures intended to bolster the debt-ridden and scandal-plagued sector, were among the top percentage losers. China Rail Construction Corp Ltd slid 3.3 percent. Before Wednesday, China Rail Construction had jumped 13.4 percent in the last seven trading sessions. It is still up 43 percent this year, after plunging 54 percent last year, 6 percent in 2010 and 14 percent in 2009.
* HSBC Holdings Plc, Europe's largest bank, slumped 2.8 percent after European Central Bank policymaker Ewald Nowotny said that restarting ECB purchases of government debt was not being currently discussed, traders said. (Reporting by Clement Tan; Editing by Chris Lewis)