A police motorcyclist in Zimbabwean President Robert Mugabe’s motorcade burned to death after crashing into a lorry in the third fatal accident since June involving the 15-vehicle convoy, notorious for sweeping through the streets at high speeds.The motorcyclist was clearing the way for Mugabe’s motorcade on Wednesday when he rammed into a moving lorry and his bike caught fire, police said on Thursday.In June, domestic media in the southern African nation reported that motorcyclists in Mugabe’s motorcade had killed two people and injured 15 others in two separate accidents.Mugabe, 88, has been in power since independence from Britain in 1980 and seeks re-election in polls expected in 2013.