The identities of the injured have not been released by police but it is understood that a woman and a man were transported to hospital. One of the victims is said to be in serious condition.
Meanwhile, more than 30 people were injured in a stampede after the gunshots rang out, with some nursing stab and chop wounds.
Prime Minister Portia Simpson Miller took the microphone immediately after the shots were fired and told comrades that “no evil will prevail”.
It is the latest political event to be marred by violence during the 2016 General Election campaign.
Three persons were shot and killed at a Jamaica Labour Party mass rally at Sam Sharpe Square, St James on February 7. Two days later, on Nomination Day, a man was shot dead and three others injured as a JLP motorcade came under intense gunfire while passing through the volatile community of Flanker in the parish.