A bomb exploded inside Pallabi police station at around 7am on Wednesday.
Confirming the matter, Pallabi Zone Assistant commissioner Firoz Kawsar said, "Five including an officer-in-charge were injured in the blast."
OC Nazrul Islam said,"A team recovered a bomb-like object from Kalshi graveyard early today. They brought it to the police station."
"We informed the Bomb Disposal Unit to neutralise it. However it exploded before the unit could reach to the police station," he added.
Four policemen and a civilian were injured in the incident.
Two of the injured police officials have been taken to Dhaka Medical College Hospital and one at National Eye Institute. Two other were given first aid.
Two more bombs were neutralised by bomb disposal unit of Counter Terrorism and Transnational Crime unit.
Dhaka Metropolitan Police's (DMP) Additional Police Commissioner Krishna Pada Roy said, "Three criminals of a local gang were arrested from Kalshi graveyard area. Two foreign pistols, three bomb-like objects and a weighing machine were seized from their possession."
"One of those objects exploded in the morning while they were waiting for the bomb disposal unit, leaving police officials and an assistant injured," he added.
The senior police official also said that they found to no militant link in the incident.
Two days ago, top police officials of different units were instructed to remain alert as police suspect extremists' links to the explosion in the capital's Paltan and the bomb-like substance recovered in Gulistan.
Last Friday night's explosion at Paltan intersection resulted in no casualties. A bomb-like object was also recovered in Gulistan the following night.
On July 19, police headquarters issued a letter regarding a possible attack by members of the so-called Islamic State just ahead of Eid in the name of their so-called mission "Bengal Uliyah" or "Bengal Khilafat," and alerted all the district SPs and other respective units.
In the letter, three embassies, international airports, Ahmadiyya/Shia community mosques, temples, pagodas, churches, policemen, police vehicles, and police infrastructure were mentioned as the possible targets of militants.