Boko Haram Using Civilians As Human Shields.

Boko Haram is using an unknown number of civilians as human shields as its fighters flee an offensive by multinational forces, a top
Nigerian official said Wednesday.

Mike Omeri, the director general of the National Orientation Agency would not say how many people are being used.

"Some say 500, some 400, some say 300," but Omeri said he was awaiting reports from authorities on the ground around Damasak, a trading town near the border with Niger that was recaptured on March 16.

Omeri stressed this was not a new incident and that the authorities are investigating.

Instead, he said that as troops advanced, Boko Haram rushed to a school where people had been held after the insurgents had seized the town late last year.

He said the fighters and those being used as shields still are in the Damasak area.

The soldiers who recaptured Damasak found the town largely deserted.

The troops from Chad and Niger who now hold Damasak have discovered evidence of a mass grave, Chad's ambassador to the United Nations, Mahamat Zene Cherif, confirmed Wednesday.

Boko Haram has killed thousands of civilians and kidnapped unknown hundreds in its fight to create an Islamic state.

The group was little known until it caused international outrage with its mass kidnapping almost a year ago of 276 girls from a government boarding school in northeast Chibok town. Dozens escaped in the first couple of days, but 219 remain missing. Their fate remains unknown and spawned the #BringBackOurGirls campaign on social media.

Nigeria's battle against the Islamic extremists is a major issue for critical presidential elections to be held Saturday. International concern has mounted along with the toll: an estimated 10,000 killed in the 6-year-old insurgency last year alone. Boko Haram has vowed to violently disrupt the elections.

International assistance desperately is needed for the thousands of Nigerian refugees who have fled the violence, the head of the U.N. refugee agency said Wednesday as he visited a camp in Cameroon.

Violence in Nigeria has forced more than 192,000 people to flee to the neighboring countries of Cameroon, Chad and Niger. But the U.N. refugee agency says the crisis hasn't drawn sufficient international support, calling it one of the most underfunded emergencies in the world.

At Cameroon's Minawao refugee camp, residents aren't getting enough to eat or drink, and there aren't enough toilets or medical supplies, Isaac Luka, a representative of the refugees, said Wednesday.

U.N. High Commissioner for Refugees Antonio Guterres said the agency will funnel more resources to Cameroon, but he noted that they have only received 3 percent of the funding necessary to run Minawao, which is home to 33,000 people.

"Every country in the world needs to understand that Cameroon is not only protecting itself, Cameroon is protecting all of us," he said.