The State-run media say two people have died of their injuries from Saturday's explosion at a presidential campaign rally.
The Chronicle newspaper says officials at Mpilo hospital confirmed the deaths. Health Minister David Parirenyatwa earlier confirmed one death; the newspaper says he cannot immediately be reached about the other.
The blast that went off shortly after President Emmerson Mnangagwa addressed a stadium crowd in Bulawayo has been called an assassination attempt. At least 49 people were injured, including both of Zimbabwe's vice presidents, but Mnangagwa was unscathed.
No arrests have been reported and officials have not laid blame.
Zimbabwe faces historic July 30 elections that are the first since longtime leader Robert Mugabe stepped down in November under military pressure.
A record 23 candidates have filed to run for president.