82 Chibok schoolgirls held captive for three years by Boko Haram were flown to Abuja to meet Nigerian President Muhammadu Buhari on Sunday, a day after they were released in exchange for several militant leaders.

“I cannot express in a few words how happy I am to welcome our dear girls back to freedom,” Buhari told the girls at his residence.

The girls, who were among the among a group of 276 schoolgirls kidnapped in April 2014, were met at the airport by Buhari’s Chief of Staff Abba Kyari and transported to a medical facility for examination.

“Welcome our girls, welcome our sisters, we are glad to have you back,” Kyari told them, saying this was “a very joyous moment.”

Military sources in the town of Banki, on the border with Cameroon, told SBS that the girls were taken to the Borno state capital Maiduguri in six military helicopters at 6:10 am (0510 GMT).

After months of negotiations between the government, the Red Cross, the Swiss government and Mustapha Zanna, a lawyer who once represented the late founder of Boko Haram, Mohammed Yusuf, families of the schoolgirls waited nervously for their names to be announced.

“Many of the parents of the girls are anxious about the identities of the girls,” Maina Mohammed, an uncle of one of the abducted girls, told the Australian Broadcasting Corporation.

The release of the schoolgirls is the largest number freed since October 2016, when Boko Haram released 21 girls after months of negotiations.

In a statement on Saturday, UNICEF Nigeria said the girls “will face a long and difficult process to rebuild their lives after the indescribable horror and trauma they have suffered at the hands of Boko Haram.”

“UNICEF calls on Boko Haram to end all grave violations against children, especially the abduction of children and the sexual abuse and forced marriage of girls.”

Boko Haram has continued to use this tactic as a weapon of war, seizing thousands of women and children over the past several years.

To date, the seven-year insurgency has killed more than 20,000 people and displaced 2.6 million from their homes.