Hundreds of women and children have been seized from Nigerian primary schools by Boko Haram militants to be used as 'human shields ' as the extremist group starts to lose its grip on the region . The Islamic militants took adults and children from primary schools in the north-eastern town of Damasak as troops from Niger and Chad approached a month ago , Mike Omeri , the Nigerian spokesman for the fight against Boko Haram , confirmed this week . When the soldiers arrived , they found the town largely deserted - with local reports suggesting as many as 500 people were taken in the raids . Scroll down for video . Kidnapped : As many as 500 women and children were taken from Damasak , in north-eastern Nigeria , as Chadian troops ( pictured ) advanced on the town , which had been held by Boko Haram for months . Mr Omeri refused to be drawn on exactly how many people had been taken by Boko Haram militants , but he was clear on the reason why they had been kidnapped . 'Boko Haram ... rushed to primary schools they took children and adults that they are using as shields to protect themselves from the menacing advance of troops , ' he said . 'They are being used as shields by Boko Haram . ' Damasak , which is near the border with Niger and had been held by Boko Haram for months , was recaptured on March 16 - but officials have only confirmed the kidnappings now . Evidence of a mass grave was also discovered by the troops from Chad and Niger , who now hold the town , Chad 's ambassador to the U.N. Mahamat Zene Cherif confirmed Wednesday . Last week , the troops found the bodies of at least 70 people in an apparent execution site under a bridge leading out of Damasak , which had been used as an administrative centre for the extremists who hope to create their own 'caliphate ' in the region . Defence : Officials believe they were taken so they could be used as human shields when troops arrived . Pictured : Chadian army celebrates entering Damasak - showing off one of Boko Haram 's flags . A 40-year-old resident , who gave her name as Fana , said fighters had rounded up captives in the main mosque before taking them out of town . She said she saved her two children by hiding them in her house . The news of the mass kidnappings and killings comes at a crucial time - just days before Nigeria goes to the polls in crucial elections . The six-year battle against the insurgents is one of the major issues voters will be considering on Saturday . Gruesome : Soldiers also discovered a mass grave near the town . Pictured : Seizing the militants ' weapons . Thousands have already lost their lives - including an estimated 10,000 last year alone - while more than 174,000 people are thought to have fled to neighbouring Cameroon , Chad and Niger as refugees . Last year , Boko Haram 's reign of terror hit the international headlines when they took 276 girls from a government boarding school . Dozens escaped in the first couple of days , but 219 remain missing . Since then , troops from Nigeria 's neighbours have started to help the country combat the militants and win back Nigerian towns . Meanwhile , Boko Haram has vowed to violently disrupt the elections .
Thousands women and children taken from Damasak primary schools . Kidnapped by Islamic militants as troops advanced on north-eastern town . Official confirms the extremists planned to use them as human shields . Mass grave also discovered in the town , used as an administrative centre .