Fourteen million people in northeast Nigeria urgently need humanitarian assistance and 75,000 children risk dying in "a few months", the United Nations warned Tuesday.
Boko Haram jihadists have laid waste to the country's northeast since taking up arms against the government in 2009, displacing millions.
UN humanitarian coordinator Peter Lundberg said the crisis was unfolding at "high speed."
"Currently our assessment is that 14 million people are identified as in need of humanitarian assistance," Lundberg told reporters in the Nigerian capital Abuja.
Out of the 14 million people who need aid, 400,000 children are in critical need of assistance, while 75,000 could die "in (the) few months ahead of us," Lundberg said.
The UN hopes to target half of the 14 million people -- a population bigger than Belgium -- with the Nigerian government working to reach the rest.
Nigerian President Muhammadu Buhari has reclaimed territory from the Islamists but the insurgency has taken a brutal toll, with over 20,000 people dead, 2.6 million displaced from their homes, and famine taking root.