Thousands of Nigerians are escaping the deadly threat posed by the terrorist group Boko Haram and fleeing into neighbouring Cameroon, the United Nations refugee agency (UNHCR) has warned.

In a press release, UNHCR cited Cameroonian authorities’ claims that some 13,000 Nigerian refugees had now crossed over from the Nigerian border state of Adamawa after Boko Haram insurgents attacked and captured the town of Mubi in late October.

The refugees fled to the towns of Guider and Gashiga in the North region of Cameroon and to Bourha, Mogode and Boukoula in the Far North, the agency added.

Insecurity has been mounting in the border regions between the two countries amid repeated cross-border attacks into northern Cameroon by Boko Haram. As a result, many Nigerians fleeing the violence have sought refuge in Cameroon.

The Minawao refugee camp, for instance, is hosting 16,282 refugees, with the population having nearly tripled in size in the past two months, according to UN estimates.

The current camp capacity is estimated at 35,000 people and further expansions are underway to accommodate the refugees already registered for transfer from the border, as well as possible additional new arrivals.

Nevertheless, despite the continuing dangers, UNHCR reported that most of the recent 13,000 refugees had already returned to their country with the city of Yola, the capital of Adamawa state, as their destination.

“The vast majority of them are women and children,” the press release observed.

“They told our teams that many families were forced to flee on foot, taking few belongings with them and walking tens of kilometres before finding safety in Cameroon.”

As the refugees re-entered Nigeria, the agency also examined claims that they had been forced to return to their country of origin, adding that it was seeking “assurances” from both States that “the return of these people was done on a voluntary basis.”

At the same time, recent violence on the Niger-Nigeria border has prompted at least 1,000 Nigerians to escape over the border into Niger’s Bosso area, particularly following last week’s capture of the garrison town, Malam Fatori, by insurgents.

The ongoing refugee crisis has seen more than 100,000 people spill over into Niger’s Diffa region since the beginning of 2014, while Cameroon is currently hosting some 44,000 Nigerian refugees. According to authorities, another 2,700 have fled to Chad.

Meanwhile, an estimated 650,000 people remain internally displaced in north-eastern Nigeria due to the insurgency.