Police also arrested the kidnappers- Sujan, 25, and Md Hannan, 23, both hailing from Chatkhil of Noakhali, and Rasel, 24, of Ramganj under Laxmipur.

The rescued boy identified as Monwar Hossain Babu, 15, son of Md Abul Kashem, is a resident of Agrabad Bahutala Colony under Double Mooring Police Station.

Sources said Sujan along with his two friends Hannan and Rasel kidnapped Monowar from outside the Bahutala Colony at around 9:30pm on Saturday when the victim went out of his house for a walk.

They took him to Karnaphuli river, got on a hired boat and phoned Monowar's parents demanding a ransom of Tk 10 lakh or they will slaughter the boy, threatened the criminals.

On information, police raided different city areas on Saturday night.

Officer in-charge of Double Mooring PS Khandaker Rezaul Karim said the kidnappers changed their destinations several times when they contacted victim's parents over phone and we also raided the areas the whole night but could not trace them.

Then the boatman helped us rescue the boy, he said.

Quoting the boatman, the OC said hearing the conversation of the kidnappers the boatman cleverly managed to bring the boat to the bank near Banglabazar area of West Madarbari at around 4:30am and contacted police over phone.

Police arrested Sujan and rescued the victim from the boat at around 5:00am.

Acting on the confession of Sujan, police arrested Rasel and Hannan from Goshaildanga of Barik Building area and Nimtala respectively.