Police quoting eyewitnesses said some 30 armed members of the PBCP attacked the five men with sharp weapons and firearms while they were harvesting paddy in the morning along with scores of other men from a marshy land of the Laxmipur Beel area.

As the attackers opened fire, four of the victims fell on the ground while others ran for cover. Later, the PBCP men slit the throats of the four men to ensure their death.

The dead were identified as Mahmud Ali, 21, Hobi Molla, 20, Hamid Molla, 50, and his son Rokon Ali, 20. Critically injured Kamrul Molla, 25, was admitted to Rajshahi Medical College Hospital.

Police said the dead too were members of another extremist group locally known as Bahini. The bodies were sent to Pabna General Hospital morgue for autopsy.

Pabna Superintendent of Police (in-charge) KM Fazlur Karim visited the spot. Police could not arrest anyone till the time when this report was filed last night.

Locals said there is a longstanding rivalry between the two outlawed groups over control of Laxmipur Beel, adding that outlaws roam freely in the remote locality in the absence of any police camp there.

In an earlier incident, Azim Hossain, 25, identified by police as a regional leader of the PBCP, was hacked to death by his rivals near Laxmipur Beel.

His body was found in the early hours of yesterday, roughly at the same spot where PBCP men attacked the four Bahini men later in the day, possibly in revenge for Azim's murder, police said.