Chamisa said violence had no place in Zimbabwean politics and took to social media to condemn such acts.
Mnangagwa has called the blast a cowardly act which would not derail the July general election, Zimbabwe's first since the downfall of Robert Mugabe after November's de facto army coup.
Presidential spokesman Mr George Charamba told state media that the president was not injured.
Several security personnel were also injured, the state-owned Herald newspaper said.
The health minister says there were no fatalities in the blast while many people are being treated in hospital.
Mnangagwa reportedly survived an attempt on his life past year when he ate poisoned food at a rally at Phelandaba Stadium in Gwanda, a small town about 550km southwest of the capital.
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Saturday's bomb attack struck only a few metres away from Mnangagwa, but the president escaped unhurt.
According to a source close to Mnangagwa, the Vice President Constantino Chiwenga and his wife sustained minor injuries.
Past votes have been marked by allegations of violence and fraud, and the United States and others have said a credible vote is key to lifting global sanctions.
Without mentioning names, Mnangagwa said there were some people who did not accept his presidency and said his "usual enemies" were behind the blast. The strongest response to violence is peace. There have been frequent allegations of assassination attempts directed at Mnangagwa and other senior politicians, though none of these have involved bombings or firearms.
Mnangagwa adopted most of Mugabe's security and bureaucratic system, fearing a complete overhaul, which the military had sought, could cause government instability and cost him votes.
The mysterious blast which rocked White City Stadium in Bulawayo on Saturday left 41 people injured, health and child care minister David Parirenyatwa has revealed.
"Mrs Chiwenga was slightly injured".