Attacks by Boko Haram Islamists in Nigeria's crisis-hit northeast have forced nearly 650,000 people from their homes, the United Nations humanitarian office (OCHA) has said.
That is an increase of nearly 200,000 since May.
Thousands have fled over Nigeria's borders into Cameroon, Chad and Niger seeking refuge from Boko Haram's relentless violence.
The attacks have killed more than 2,000 civilians this year and left scores of villages destroyed.
Relief workers have so far avoided setting up refugee or internally displaced persons (IDP) camps.
However, some fear camps may soon become necessary, especially in Nigeria, as the security forces struggle to contain the escalating Islamist violence.
OCHA said 436,608 people have been displaced in the states of Adamawa, Borno and Yobe, which were placed under emergency rule in May 2013.
The agency put the IDP figure at 250,000 in May this year.
Another 210,085 have fled their homes in areas neighbouring the state of emergency zone, bringing the total number of people displaced by Boko Haram unrest to nearly 650,000, OCHA reported.
The Islamist insurgents, who are seeking to create an Islamic state in the country's predominantly Muslim north, have killed more than 10,000 people since 2009.
The military has for more than a year been waging an offensive in the northeast aimed at crushing the uprising.
However, the campaign appears to have yielded few gains and the military's tactics have been harshly criticised.
The latest report of massive abuses by Nigeria's military came yesterday from Amnesty International, which released videos that appeared to show the security forces and allied vigilantes carrying out extrajudicial executions, including by slitting people's throats.
Nigeria's defence ministry said it was taking Amnesty's allegations "very seriously" and would launch an investigation.
The UN refugee agency (UNHCR) reported that about 1,000 people trying to escape the fighting had fled to an uninhabited island on Lake Chad across Nigeria's northeastern border.
"The group, mainly women and children, is in urgent need of food, water, shelter and medical care," the UNHCR said.
They reached the remote island of Choua on Thursday after fleeing a Boko Haram attack in their hometown of Kolikolia, according to the refugee agency.
Chad has pledged to send two helicopters to the island to help evacuate the Nigerian refugees to a nearby area where they can be temporarily settled with host communities, the UNHCR added.