At least 9,500 people have returned to Nigeria from Cameroon since the Cameroonian government said last month it will expel unregistered Nigerian refugees as part of the fight against Boko Haram.

Some of those who have returned claimed being mistreated by the Cameroonian authorities, including being packed in trucks leading to suffocation and alleged deaths of some them.

The National Emergency Management Agency official in charge of camps, Saad Bello, said that 9,500 people have come through the Sahuda border post in Adamawa state and many of the returnees are from Borno state which has seen constant attacks by Boko Haram extremists.

Nearly 20,000 people have died and almost 2 million have been driven from their homes during the Islamic extremist group's six-year-old uprising.