Up to 10,000 civilians have been forcibly relocated because of a military operation against Boko Haram in northeast Nigeria, the UN said on Thursday, calling for better protection.
But the UN said five times as many were forced to flee.
"The military ordered the immediate departure and forced the relocation of up to 10,000 civilians in the middle of the night, without prior warning," it said in a statement.
"Some people said they arrived in Maiduguri with nothing, not even with shoes on their feet."
The jihadists have in the last few weeks been hit by intensive air and ground offensives from coalition forces involving Nigeria, Chad and Cameroon against militant camps in Lake Chad, according to military sources and militia groups.
But there will be fresh concern about the effects of the conflict on civilians, after nearly 10 years of fighting, more than 27,000 deaths and 1.8 million made homeless.
Previous mass displacements of civilians have forced them into already overcrowded camps for the internally displaced in Maiduguri, putting pressure on the authorities.
"The United Nations is urging the government to urgently provide safety, shelter, food, water and medical care to the displaced civilians, in addition to information about when they will be allowed to return home," said Kallon.
In January, ISWAP - the Islamic State West Africa Province, the IS-linked faction of Boko Haram -- sent letters to Jakana and Mainok residents telling them to vacate their homes for an impending raid on the military.
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