The group allegedly headed by Golam Sabbir was enraged as policemen did not go to his land to stop an 'encroacher' from fencing it, without seeing a court order.
Superintendent of Police S A Reza said Sabbir and his men then assaulted those on duty in the outpost and they were hospitalized yesterday.
Sabbir and his two sons were arrested.
Reza said the Sabbir had purchased a piece of land at Jiagachi under Karandighi police station and he suspected that owner of the neighboring land encroached into his portion while trying to fence it.
However, when he along with others went to Dalkhola outpost to ask policemen to go to the land, he did not bring the order of the executive magistrate, Reza said adding the policemen wanted to see the order before taking any action.
Sabbir and his men got angry at this and beat up the five policemen.