Chibok schoolgirls kept captive by Boko Haram for three years pictured for first time since their release

Nigeria's President Muhammadu Buhari sits among 82 rescued Chibok girls (Photo: AFP)

Schoolgirls who were imprisoned by Boko Haram for more than three years have been pictured for the first time since their release.

Dozens of Chibok schoolgirls being kept captive by Islamist militants, were set free on Saturday after years of tense negotiations.

Nigerian President Muhammadu Buhar has expressed joy at meeting the 82 girls, as he shared photos of them on social media.

In a statement on Facebook, he wrote:

"I cannot express in a few words how happy I am to welcome our dear girls back to freedom.

I am very pleased to have personally met you and let me assure you that the presidency will personally supervise the performance of those entrusted with your welfare and commitments made by the Federal Government on your health, education, security and general well-being.

No human being should go through this kind of ordeal.

The security agencies and state governments should continue to provide special protection to educational institutions vulnerable to this kind of outrage especially in remote areas.

I congratulate you and your parents on your safe return."

In 2014 around 220 students were abducted from a secondary school in the north eastern town of Chibok, sparking a global campaign 'bringbackourgirls'.

The campaign was supported by then U.S. First Lady Michelle Obama and list of celebrities.

About 21 Chibok girls were released in October in a deal brokered by Switzerland and the International Red Cross.

A handful of others have escaped or been rescued. But about 195 were still missing.

Last month President Muhammadu Buhari said in a statement the government was "in constant touch through negotiations.

For more than two years there was no sign of the Chibok schoolgirls.

But the discovery of one of the girls with a baby in May 2016 fuelled hopes for their safety, with a further two girls found in later months and a group released in October.

United Nations have stressed the Chibok girls are not the only ones who have suffered violence at the hands of Boko Haram.

At least 2,000 boys and girls have been kidnapped by Boko Haram since 2014, with many used as cooks, sex slaves, fighters and even suicide bombers, according to Amnesty International.

The use of children as suicide bombers by the militants is also on the rise in the Lake Chad region with 27 such attacks recorded in the first three months of 2017 compared to nine for the same period in 2016, the U.N. children's agency UNICEF said.

Despite having lost most of the territory it held in 2015, Boko Haram continues to wage its insurgency, which is now in its eighth year.