Confirmed reports say that about 2,500 Nigerians have arrived in Diffa in southern Niger in the past few days.
The heavy battle between the military and the Boko Haram has continued to displace thousands of people on both sides of the country's border with Cameroon to the northeast and Niger to the north; the U.N. refugee agency (UNHCR) said on Tuesday.
Boko Haram has fought tooth and nail to gain territories over the past 6 years.
At least 13 people were killed in a twin suicide attack by suspected militants in the Cameroonian border town of Fotokol on July 12. The volatile situation is pushing many people to leave the area, the UNHCR said.
Many of those moving south, away from the sites of recent attacks, are going to the Minawao camp in Cameroon, where around 100 people arrive each day, UNHCR spokesman Leo Dobbs told a news briefing in Geneva on Tuesday.
"This particular movement is people who fled earlier (...) and have been in the area for a while. Life is difficult up in the border areas", he said.
More than 12,000 refugees in the Far North Region of Cameroon, where UNHCR access is limited, are not on authorities' radar, Dobbs said, adding that many fear registration is a precursor to deportation to Nigeria.
"To counter this fear, we and the government are in the process of consulting the refugees in the border area about where they want to go," he said.
They will be given the choice of returning to safe areas of Nigeria or going to Minawao camp.
In a separate development, authorities have reported the arrival of 2,500 Nigerians in Diffa in southern Niger in the past few days, the U.N. refugee body said.
This follows fighting around the Nigerian border town of Damasak, with refugees arriving in the villages of Chetimari and Gagamari on the Nigerien side of the border across which more than 100,000 Nigerians are reported to have fled since mid-2013.