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GENEVA (Reuters) - Nigerian troops forced the entire population of a town of 10,000 people in northeastern Borno state to relocate without warning on Monday, the United Nations said on Thursday.

A U.N. statement said soldiers moved the people of Jakana to a camp in the city of Maiduguri about 40 km (25 miles) away, some arriving with “nothing, not even shoes on their feet”.

The armed forces were conducting an operation to flush out Islamist Boko Haram insurgents, Abdulmalik Bulama Biu, a commanding officer in the northeast, said without elaborating.

The military and government returned nearly 5,000 Jakana residents to the town on Thursday, Nigeria’s National Emergency Management Agency said on its official Twitter account.

Jakana residents said the military was screening the population for members of Boko Haram.

The northeast of Nigeria, sub-Saharan Africa’s biggest energy producer, is the main battleground in its decade-long fight against Boko Haram and fellow Islamist insurgent group Islamic State West Africa Province.

A surge in militant attacks in December in which towns and military bases were overrun put tens of thousands of civilians to flight into Maiduguri, swelling the population of existing camps.

“The entire town of Jakana was emptied, and people were forced to move to Maiduguri with very little time to collect personal belongings,” Edward Kallon, U.N. humanitarian coordinator for Nigeria, said in the statement.

Last June, the Nigerian government ordered thousands of people to leave the relative safety of their camp in Maiduguri to live in a town in an unsafe area as pressure mounted to show progress in the war against militants ahead of elections, sources familiar with the situation said. In September, the town was attacked, forcing the population to flee.