Singapore shares edged lower on Monday, dragged down by losses in Sembcorp Marine Ltd which hit a six-week low after posting lower-than-expected first-quarter earnings. The benchmark Straits Times Index was down 0.2 percent at 3,245.69 by 0506 GMT. MSCI's broadest index of Asia-Pacific shares outside Japan dipped 0.3 percent. Shares of Sembcorp Marine fell 2.5 percent to an intra-day low of S$3.96, their lowest since March 21, after the offshore drilling rig builder posted a 3.1 percent increase in first-quarter net profit, which nonetheless undershot market expectations. CIMB downgraded its rating on Sembcorp Marine to "hold" and cut its target price to S$4.30 from S$5.10, citing a shortfall in ship repair and rig building revenue.