Following this attack, police detained Harun-or-Rashid Truman, general secretary of Bhola district unit BNP, said Shafin Mahmud, additional superintendent of Bhola Police.
BNP leaders and activists brought out a procession in the area marking the party’s 40th founding anniversary, to be celebrated on Saturday, in the evening.
Several crude bombs were hurled from the procession targeting the policemen who were on duty in the area around 8 pm, leaving four of them injured, police said.
District Jubo Dal Tariqul Islam said some leaders and activists of the party brought out a procession around 7:30 pm to observe the founding anniversary.
Later, they held a meeting at its central office and heard the sound of blasts, he added.
Meanwhile, additional police forces were deployed in different important points of the district town, said ASP Shafin Mahmud.