Nairobi – At least 20 people in Tanzania were trampled to death at an open-air evangelical Christian church service in the north of the country, officials said on Sunday.Government official Kippi Warioba, district commissioner in the northern town of Moshi, said he feared the number of dead could still rise from the accident, which took place on Saturday afternoon."So far, 20 people have died, but the death toll could increase as there were also wounded," Warioba told AFP.The tragedy happened when a crowd of worshippers was attending a prayer ceremony on Saturday led by the popular preacher, Boniface Mwamposa, who heads the Arise and Shine Ministry Tanzania.Holy oilThe stampede occurred when Mwamposa, who calls himself the "Apostle", poured what he said was holy oil on the ground and the crowd surged forward to touch it in the hope of being cured of sickness, witnesses said."The apostle Boniface Mwamposa poured sacred anointing oil on the ground," one witness, Jennifer Temu, told AFP."Dozens of people immediately fell being jostled and trampled, and some died. We have counted 20 people killed – but there are also wounded.""It was horrible, people trampled on mercilessly, jostling each other with elbows," said another witness, Peter Kilewo."It was like the preacher had thrown bundles of dollars about... and there were all these deaths!"