Njaba is a Local Government Area of Imo State, Nigeria. Its headquarters is located in the town of Nnenasa. It has an area of 84 km² and a pop…Njaba is a Local Government Area of Imo State, Nigeria. Its headquarters is located in the town of Nnenasa. It has an area of 84 km² and a population of 143,485 at the 2006 census. The 2011 density projection is 2,004.5 inhabitants/km². The postal code of the area is 474.