WASHINGTON, May 12 (Reuters) - U.S. consumer prices increased more than expected as booming demand amid a reopening economy pushed against supply constraints, which could fuel financial market fears of a lengthy period of higher inflation. The consumer price index jumped 0.8% last month after rising 0.6% in March, the Labor Department said on Wednesday. Excluding the volatile food and energy components, the CPI soared 0.9%. The so-called core CPI rose 0.3% in March. Economists polled by Reuters had forecast the overall CPI climbing 0.2% and the core CPI rising 0.3%. (Reporting by Lucia Mutikani; Editing by Andrew Heavens)