A girl who was kidnapped by Nigerian terror group Boko Haram three years ago has decided to remain in captivity to stay with her husband, the government has said. Earlier in May, the group released 82 girls in exchange for prisoners following negotiations that involved also the Swiss government.

It is believed the group had agreed to free 83 girls, but one of them refused to leave to stay with her husband, believed to be one of the militants.

"One of the girls refused to join the released girls. She said 'I am happy where I am. I have a husband,'" Garba Shehu, spokesperson for President Muhammadu Buhari, told news agency AP on 9 May.

Those freed were part of a group of more than 200 schoolgirls kidnapped from the Chibok village, in the restive Borno state, northeastern Nigeria, in April 2014.

At least 21 Chibok girls were released last October in another deal brokered by Switzerland and the Red Cross. It is believed 114 girls are still in Boko Haram custody.

The government has released the names of those who were freed and families are travelling to the federal capital of Abuja to reunite with the girls.

Although the Chibok abduction was not the first mass-kidnapping carried out by Boko Haram, it was the only one that attracted international outrage. It led to the creation of the global movement Bring Back Our Girls, which shone a spotlight on the deadly insurgency of Boko Haram that had previously been under-reported.

The Islamist outfit fights against Western influence in Nigeria and aims to impose its version of Sharia law throughout occupied territories. In 2016, the group allied with Isis. However, when Isis replaced Abubakar Shekau as leader with Abu Musab al-Barnawi, a former Boko Haram spokesperson, the group split in to at least two factions.

The UN says at least 20,000 people have died in Nigeria and neighbouring states since the Boko Haram insurgency became violent in 2009. The conflict has also displaced at least 2.1 million people.

The group used to control territories the size of Belgium. However, Nigeria's ongoing military operation, Lafiya Dole, and a regional offensive – consisting of 8,700 troops from Nigeria, Niger, Chad, Cameroon and Benin – have scored some success, with soldiers recapturing key territories and releasing thousands of civilians held captive by the group.

Although the release of the girls has been widely welcomed, some analysts have pointed out it does not mean the fight against the insurgents is now over.

Nigeria up close: Check out our Flipboard magazine