Escalating violence in northwest Nigeria blamed on armed bandits has forced more than 40 000 people to flee across the border into Niger over the last 10 months, the UN said on Friday.
However, the surge in kidnappings, killings, sexual violence and other unrest in this area is not known to be linked to Boko Haram's Islamist insurgency, which is concentrated in northeast Nigeria.
"People are seeking safety from indiscriminate attacks unleashed by organised armed groups on men, women and children alike," the United Nations refugee agency said in a statement.
UNHCR spokesperson Babar Baloch told reporters that the agency did not have clear information on the perpetrators of the violence in the states of Sokoto, Zamfara and Katsina, while Nigeria's government has blamed armed bandits.
The UN said that 2 500 refugees crossed into Niger on September 11 alone after an attack targeting civilians.
"As the security situation continues to deteriorate in Sokoto State, we are expecting more refugees to arrive in Niger," the statement said.
UNHCR said it was ramping up assistance to the remote border area on the Niger side, including more staff and fresh shipments of supplies.