About $38 million dollars (30 million euros) are needed to help some two million people made homeless by deadly floods that have ravaged Nigeria, the UN humanitarian agency said Friday.

"The humanitarian community in Nigeria has presented a response plan for $38 million to respond to the humanitarian needs after the severe flooding in Nigeria in recent weeks," Jens Laerke, spokesman for the UN Office for the Coordination of Humanitarian Affairs (OCHA), told reporters in Geneva.

Nigeria estimates that the now slowly receding floods have killed 363 people and affected another 7.7 million, of whom 2.1 million have been displaced from their homes.

"There is severe or very severe food insecurity in many places," Laerke said, adding there was also a "high risk of epidemics" because of a lack of access to clean water and adequate sanitation.

The UN children's agency UNICEF also said the spread of water borne and water-related diseases like diarrhoea and malaria was a top concern.

Two thirds of Nigerians displaced by the floods were getting drinking water from ponds, streams or unprotected wells, while almost 70 percent were forced to defecate in the open, UNICEF spokeswoman Marixie Mercado told reporters.

UNICEF said it had already reached 258,000 displaced people in 17 camps with emergency supplies.

The Red Cross on Friday also appealed for urgent international aid for victims of the floods, which it called Nigeria's worst in four decades.

"We desperately need to bring the world's attention to this ongoing silent emergency," said Bello Hamman Diram, secretary general of the Nigerian Red Cross Society, according to a statement from the International Federation of Red Cross and Red Crescent Societies.

"There are very few humanitarian actors here in Nigeria... for us to be able to assist those who are most vulnerable, we require financial aid. Without it, the future for hundreds of thousands of Nigerians will remain very precarious."

The statement said it was appealing for at least 2.8 million Swiss francs ($3 million, 2.3 million euros) to provide supplies such as blankets, water and latrines.

The Red Cross statement however provided far lower figures than those given by Nigeria, saying that since heavy rains began in late August, flooding had damaged or destroyed close to 27,000 homes as well as farmland, schools and health care centres.

More than 422,000 people have been affected across 11 of Nigeria's 36 states, it said.

Late Thursday in Abuja, President Goodluck Jonathan launched a national committee, headed by Africa's richest man, Aliko Dangote, to raise funds for the flood victims.

Nigeria often faces flooding during the rainy season, but heavy downpours and overtopped rivers have inundated vast areas of Africa's most populous nation and largest oil producer this year.