The Doctors Without Borders aid group says it has witnessed Cameroon's military returning Nigerian refugees to their country as the number of people fleeing hunger and Boko Haram extremist violence there has mounted.

The medical charity said Wednesday its teams have observed refugees being returned to Nigeria several times last year and this year.

A Cameroon government spokesman strongly denies the allegations. Issa Tchiroma calls them "particularly unjust."

Doctors Without Borders, also known by its French acronym MSF, described a dire humanitarian situation in Nigeria's northeast, saying health facilities are not functioning and it is too dangerous for patients to travel.

The northeast is home to Boko Haram, which continues to carry out suicide bombings even as Nigeria's military pushes it from strongholds. The insurgency has left millions facing hunger.