"That act of terrorism that happened in Bulawayo is nothing", he added. "It doesn't undermine the security of the country, but we are jolted". The protection at Chiwenga's rally appeared no heavier than normal, with no security checks for those attending.
She said comprehensive investigations are underway on the blast which occurred shortly after Zimbabwean President Emmerson Mnangagwa had finished addressing the rally.
"As a long standing friend of Zimbabwe, Kenya sends its message of goodwill to President Emerson Mnangagwa and the people of the Republic of Zimbabwe, and urges restraint during the campaign and electioneering period because political competition should not fracture Zimbabweans but should be a measure to deepen their democratic credentials", the President notes.
Those policies were cornerstones of Mugabe's near four-decade rule, but the ruling ZANU-PF says Zimbabwe is at a critical stage of its transition and needs an experienced hand like Mnangagwa at the tiller.
Plain-clothes police conducted random stop-and-search operations on the streets of Bulawayo while armed police mounted check points along the main highway leading out of the city.
"While the majority of the nation is united behind this dream, there are those who feel threatened by the steps we are taking, they do not want the open and progressive Zimbabwe we are thriving for".
Several security personnel were also hurt, the state-owned Herald newspaper said. No arrests have been reported and officials have not laid blame.
Mnangagwa told state broadcaster ZBC, without elaborating, that those responsible must have come from "outside Bulawayo".
Mnangagwa added, "However, my fellow Zimbabweans I assure you they will not succeed, we will not turn back; the forces of progress can not be stopped".
Mnangagwa has vowed a credible election, the first since longtime leader Robert Mugabe stepped down in November under military pressure.
Elections in Zimbabwe have been marred in the past by violence and charges of electoral fraud.
Twenty-three candidates have filed to run for president at the election.