An estimated 1 million people have been affected from heavy flooding in Nigeria's northeastern city of Maidguri, a government official said on Wednesday.

Babagana Zulum, the governor of Borno State, told journalists the estimate was based on preliminary assessment conducted by the government after the flood hit Maiduguri on Tuesday and caused devastation, the worst in three decades.

"The floods covered one third of the city, affecting over 1 million people. It is very devastating," Zulum told journalists while distributing cash and food to thousands of displaced persons at a camp.

He said over 100,000 people are displaced, even as search and rescue efforts continue.

"We are distributing money and food to head of each of the families as temporary measure to cushion the impact," he said, adding that the government plans to constitute a health team to prepare response for possible emergencies after the waters recede.

He also blamed collapse of a dam in the city's outskirts, and overflow of water released from neighboring African nations of Niger and Cameroon for the situation.

The flood washed away animals at zoo, damaged houses, schools, hospitals, government offices, as well as commercial centers and worship centers.