Kawsar Ahmed, local BNP leader, claimed that a group of Awami League men equipped with sticks swooped on the BNP activists during an election campaign in front of Poricharja Hospital around 6 pm.
The miscreants also hurled brick chips at the BNP campaigners.
The attack was launched when Gayeshwar, a BNP standing committee member, was going to Kadamtali from Chunkutia, leaving 25 people, including Gayeshwar, former upazila BNP secretary Advocate Sultan Naser, South Keraniganj thana unit general secretary Abu Bakar Siddique Kawser and Dhaka district Jatiyatabadi Chhatra Dal president Haji Masum, injured.
Gayeshwar got his skull fractured in the attack and he was kept confined to a shop with his head profusely bleeding, said witnesses.
Later, the attackers left the spot after the journalists rushed in on information, said BNP leader Abdus Salam Azad.
The injured were first taken to Mitford Hospital from where they were shifted to Islami Bank Hospital at Kakrail in the capital.
Shah Jamal, officer-in-charge of Keraniganj South Police Station, said they have heard the news.