Photojournalist Gulbar Ali Jewel, Daily Ittefaq's Kabil Hossain and Prothom Alo's Shahidul Islam Dukhu were wounded at the city's Sagarpara on Thursday noon.
Jamaat's chief Matiur Rahman Nizami was among the 14 sentenced to die by a court in Chittagong for their roles in the smuggling of a huge cache of weapons ranging from AK-47s to rocket launchers, in 2004.
Jewel said crude bomb splinters had pierced their legs. They were given first aid at a local hospital.
Prothom Alo's Shahidul said, "Jamaat and Shibir men were leaving after their rally, when they hurled bombs at waiting journalists."
Boalia Model Station OC Ziaur Rahman Zia said supporters of Jamaat and Shibir, who held brief rallies and processions, ran away before police arrived.
They hurled bombs as they fled.
Witnesses said Jamaat supporters brought out a procession in Sagarpara as soon as the verdict was announced around noon.