Flooding in Nigeria since July has killed 363 people and displaced 2.1 million in what the president has called an unprecedented situation in Africa's most populous nation, officials said Monday.

The National Emergency Management Agency said, based on information gathered on floods from July 1 to October 31, "363 persons died while 18,282 people were treated for injuries they sustained during the flooding."

A total of 7.7 million people were affected by flooding during the period, of which 2.1 million were officially registered across the country as internally displaced persons, the statement said.

Last month, severe flooding temporarily cut Nigeria's oil output by around 500,000 barrels per day, or some 20 percent of total production in Africa's largest crude producer, an industry regulator has said.

The Red Cross said in early October that flooding across Nigeria had killed at least 148 people and displaced more than 64,000.

President Goodluck Jonathan's government has pledged $110 million to mitigate the damage caused by "unprecedented" floods. He also set up a team to raise money to assist the victims.

The rainy season in Nigeria, whose population is some 160 million, runs roughly from March to September, though rains continued into October this year.

The largest cities in Nigeria are overcrowded, with many residents living in haphazardly constructed slums. Drainage systems are also often poorly maintained and contribute to the problem.

Overtopped rivers have inundated vast areas of the country this year.

In 2010, flooding affected roughly half a million people in two-thirds of Nigeria's 36 states.