Cars and motorcycles were also reportedly burnt by the invaders.
The attacks took place on Monday, it was learnt.
The three communities attacked were Obegu, Amazu and Egedege, all in Íshíelu council area of the state.
The reason for the attack was not known at press time.
Many others sustained various degrees of injuries.
The attackers, it was further learnt, also looted the communities.
An unnamed Methodist Church priest was said to be among those killed.
Police spokesperson Loveth Odah confirmed the attack.
Governor David Umahi directed security agents in the state to apprehend the attackers.