A blast rocked a vegetable market in Somalia’s third-largest city, killing at least eight people and wounding at least 15, witnesses and a police official said Monday.Baidoa police officer Abdullahi Ahmed said the blast was caused by a roadside bomb. Witness Nur Yusuf said the bomb was concealed in a thermos placed along the street where he sells vegetables."So far, we know eight people died and fifteen others were injured,” Ahmed said. "The death toll may rise, but it was a cowardly attack targeting civilians — we have arrested one suspect after the blast.”Eyewitness Fadumo Haji said she saw the carnage."They killed innocent and poor people,” she said.Baidoa was a major base for Somali militants al-Shabab until Ethiopian troops and Somali soldiers seized the key town in February. Some 100 soldiers are now being sent to Baidoa as an advance team for 2,500 troops soon to be deployed there. The AU troops will be stationed alongside Ethiopian troops already in Baidoa.A blast last week in the capital ripped through the national theater, killing 10 people and wounding many more. Among the dead were two top sports officials.