At least 12 fishers were injured on the fishing trawler FB Mim near Kuakata in the Bay of Bengal early on 5 August.
The incident occurred near the Khamba buoy-light area, about 28 kilometres southeast of Kuakata.
Trawler owner Ibrahim alleged that another trawler rammed FB Mim as it was returning to shore after fishing.
He said 20 to 25 armed men then boarded the vessel, assaulted the crew with locally made weapons and took fish, nets and fuel.
Ibrahim estimated the value of the stolen property at about Tk350,000.
The injured fishers are from the Dakkhin Aicha area of Char Fasson in Bhola, and the trawler had left Char Fasson with 14 fishers last Thursday, Ibrahim said.
Three injured fishers were taken to Kuakata's 20-bed hospital.
The trawler's helmsman, Ayub, 40, was admitted to a hospital in Kalapara with serious injuries.
The remaining injured fishers received first aid locally.
Payra Port naval police outpost officer-in-charge Nayan Karkun said the area was not under the unit's direct jurisdiction.
Karkun said naval police had checked on the fishers and arranged treatment.
The evidence does not identify the alleged attackers or establish whether any case, arrest or investigation has followed.