The incident occurred in a village in Subarnachar Upazila early Thursday, said Charjabbar Police Station OC Nizam Uddin.
Police have yet to identify the victims.
An initial police investigation found that cattle had been stolen from the village in the past few days, leading the villagers to set up a watch.
“Around dawn a pickup carrying seven to eight people parked near Kacchabia village. The locals surrounded and began to beat the men. Four were killed in the clash.”
Two others were injured in the brawl. Police recovered the wounded and sent them to Noakhali Sadar Hospital for treatment.