Footage circulating on social media showed an explosion and plumes of smoke around the president as he descended stairs from the podium at the White City stadium.
Zimbabwe's President Emmerson Mnangagwa survived a blast at a ruling ZANU-PF party rally on Saturday, while one of his vice-presidents and two other party officials were injured.
A number of other people were also hurt in the explosion during the election campaign event in Zimbabwe's second city Bulawayo, according to witnesses, but no official toll has yet emerged.
Footage circulating on social media showed an explosion and plumes of smoke around the president as he descended stairs from the podium at the White City stadium.
Images broadcast on Zimbabwean TV showed scenes of chaos and medics fighting to save those wounded by the blast.
Vice President Kemo Mohadi, ZANU-PF chairwoman and cabinet minister Oppah Muchinguri-Kashiri and party secretary Engelbert Rugeje were injured, state broadcaster ZBC said.
"The president was evacuated successfully. He is at state house in Bulawayo," said Mnangagwa's spokesman George Charamba.
"We suspect it's an explosion, certainly it was close to the VVIP stage."
Mnangagwa had been in the city to campaign for votes ahead of nationwide elections due on July 30.
"There was an explosion as Mnangagwa was leaving the stage. People started running in all directions and then immediately the president's motorcade left at a very high speed. Suddenly soldiers and other security details were all over the place," said an AFP correspondent at the scene.
"The whole area close to the podium was then cordoned off but several people appeared to have been injured," added the reporter.
Injured ZANU-PF supporters were taken to a nearby hospital where one man wearing a blood-stained party T-shirt waited for treatment.
Home Affairs Minister Obert Mpofu confirmed the "unfortunate incident" adding: "There were some injuries but I am still to get full details but as you are aware this happened close to the (president)".
Bulawayo has long been seen as a bastion of opposition to the ZANU-PF and it was Mnangagwa's first rally in the city.
The polls in five weeks will be the first since Zimbabwe's veteran leader Robert Mugabe resigned following a brief military takeover in November last year after 37 years in power.
The intervention by the army was led by Chiwenga who was then head of the armed forces.
The vote will be a key test for Mnangagwa, 75, who succeeded the 94-year-old autocrat and remains untested at the ballot box.
He has pledged to hold free and fair elections as he seeks to mend international relations and have sanctions against Zimbabwe dropped.Previous elections in Zimbabwe have been marred by electoral fraud, intimidation and violence, including the killing of scores of opposition supporters in 2008.
Mnangagwa has been accused of involvement in the Gukurahundi massacres of the 1980s that claimed the lives of around 20,000 regime opponents in the country's southwest where Bulawayo is situated.
Twenty-three candidates, the highest number in the country's history will contest the presidential race.
The main competition will be between Mnangagwa and the main opposition Movement for Democratic Change's leader, 40-year-old Nelson Chamisa.
