82 schoolgirls who were kidnapped by Boko Haram have been released after more than three years in captivity.

They are the largest group yet to be released after years of tense negotiations between the government and the terrorist group, a Nigerian government spokesman said.

The girls were among about 220 students abducted from a secondary school in the northeastern town of Chibok in 2014, sparking a global campaign #bringbackourgirls supported by then-U.S. First Lady Michelle Obama, and a host of other celebrities.

A Boko Haram video shows the girls, wearing the full-length hijab and praying in an undisclosed rural location

Enoch Mark, a Christian pastor whose two daughters were among those kidnapped, said he was told of the release by the Bring Back Our Girls pressure group and an official in Maiduguri.

He added: 'This is good news to us. We have been waiting for this day. We hope the remaining girls will soon be released.'

Bring Back Our Girls said it was awaiting an official statement but added: 'Our hopes and expectations are high as we look forward to this news being true and confirmed.'

Boko Haram fighters stormed the Government Girls Secondary School in the remote town of Chibok on the evening of April 14, 2014 and kidnapped 276 girls.

Fifty-seven managed to escape in the hours that followed but the remaining 219 were held by the group.

21 Chibok girls were released in October (pictured) in a deal brokered by Switzerland and the International Red Cross

Boko Haram leader Abubakar Shekau claimed in a video message that they had converted to Islam.

The kidnapping brought the insurgency to world attention, triggering global outrage that galvanised support across the globe.

21 Chibok girls were released in October in a deal brokered by Switzerland and the International Red Cross, while a handful of others have escaped or been rescued.

However, a large number of the girls are still missing.

'The government will soon release an official statement,' a government spokesman said.

Last month President Muhammadu Buhari said in a statement that the government was 'in constant touch through negotiations, through local intelligence to secure the release of the remaining girls and other abducted persons unharmed'.

The girls were taken from a school in Chibok in the remote northeastern Borno state where Boko Haram has waged an insurgency aimed at creating an Islamic state that has killed thousands and displaced more than 2 million people.

Campaigners chant slogans during a protest last month calling on the government to rescue the remaining kidnapped girls

Although the Chibok girls are the most high-profile case, Boko Haram has kidnapped thousands of adults and children, many of whose cases have been neglected.

The militants have killed more than 20,000 people and displaced more than 2 million during their insurgency aimed at creating an Islamic caliphate in northeast Nigeria.

Despite the army saying the insurgency is on the run, large parts of the northeast, particularly in Borno state, remain under threat from the militants, and suicide bombings and gun attacks have increased in the region since the end of the rainy season late last year.