Doctors Without Borders (MSF) said Friday it was providing emergency help after 33 children died in a camp housing people displaced by the Boko Haram insurgency in northeast Nigeria.
MSF said that the children died between August 2-15 in Bama, once the second-largest town in the ravaged state of Borno but now a humanitarian hub.
"They are dying due to malnutrition," said Lisa Veran, MSF spokesperson in Paris.
Children are arriving to the camp in "critical condition" and their health is worsening in the absence of proper medical care, MSF said in a press statement.
Thousands of people are being sent back to Bama by the Nigerian government, which claims that Boko Haram Islamists are no longer a potent threat.
Since April, more than 10,000 people have returned, putting pressure on a facility that hit maximum capacity of 25,000 at the end of July, MSF said.
The "assistance provided is not keeping up with the number of IDPs (internally displaced people)," it warned.
In June, President Muhammadu Buhari, who is seeking re-election next year, said that Nigeria's remote northeast is in a "post-conflict stabilisation phase".
But a recent surge in attacks has highlighted the deteriorating security situation there. Soldiers have started protesting following a series of bloody Boko Haram attacks on military bases in recent months.