The UN says it estimates there are more than 350 million illegal light weapons in Nigeria. The UN Regional Centre for Peace and Disarmament in Africa said this accounted for 70% of illicit small arms in West Africa.
Some of the weapons are said to have originated in Mali and Libya, where there are ongoing conflicts.
The UN said the presence of so many illegal arms in Nigeria threatened its existence. Nigeria is affected by three separate conflicts - an Islamist insurgency in the north-east, militancy in the oil-rich Niger Delta, and clashes between nomads and farmers, BBC reports.