Twenty people, mostly women and children, were trampled to death on Monday during the distribution of food and money among refugees in Diffa, southeast Niger.
The aid workers confirmed the incident, adding that about 10 people were injured.
The region has been repeatedly hit by attacks by Nigeria’s Boko Haram jihadist group since 2015.
United Nations figures released in October show that the region hosts some 119 000 Nigerian refugees, 109 000 internally-displaced people and 30 000 Nigeriens who have come home from Nigeria because of the instability in the northeast.
The aid being distributed was given by Babagana Umara Zulum, the governor of Borno state in northeast Nigeria.
He had come to the region to visit the refugee camps, and had already left the town when the stampede occurred.
A source said thousands of people heard about the handout and left the camps, sometimes travelling up to 100 kilometres to get to Diffa.
“Even ordinary inhabitants of Diffa rushed there in the hope of getting the handout,” one resident said.