At least 44 people have now died in a cholera outbreak in northeast Nigeria, the United Nations said Monday, calling for nearly $10 million to keep the disease from spreading.

"To date, the outbreak has claimed at least 44 lives, out of close to 2,300 confirmed and/or suspected cases," the world body said in a statement.

About $9.9 million (8.3 million euros) is needed as part of the relief effort, the UN Office for the Coordination of Humanitarian Affairs (OCHA) said.

The first cholera case was identified in Borno State on August 16 and has since spread, mainly in camps for those displaced by the Boko Haram insurgency.

Water-borne diseases are a constant threat because of a lack of adequate sanitation as well as stagnant groundwater during the current rainy season.

The agency's deputy humanitarian coordinator for Nigeria, Peter Lundberg, said that despite new treatment centres and sanitation measures, more needed to be done.

"The camps for displaced persons are congested, there is not enough water, sanitation facilities are poor, and the health care system is weak," he said. 

"We must tackle this urgently to avoid preventable suffering and loss of life."

Additional funding would help to implement a cholera response and prevention plan in the coming months, including providing access to clean water and a vaccination programme.

Northeast Nigeria is already in the grip of a humanitarian crisis caused by the Boko Haram insurgency, which has killed at least 20,000 people and displaced more than 2.6 million.

The UN's head of humanitarian affairs and emergency relief, Mark Lowcock, said last week that the threat of famine caused by the conflict's impact on farming had been averted.

But 8.5 million people in the northeast, out of 17 million in the wider Lake Chad region comprising Nigeria, Cameroon, Chad and Niger, needed humanitarian assistance, he said.