Boko Haram released 21 Chibok schoolgirls on Thursday, two and a half years after they were kidnapped from their school in northeastern Nigeria.

The Nigerian government released a statement, taking credit for the girls release but did not reveal any details, such as whether a ransom had been paid to the kidnappers, or prisoners exchanged.

"The release of the girls ... is the outcome of negotiations between the government of President Muhammadu Buhari and Boko Haram brokered by the International Red Cross and the Swiss government," the statement said. "The negotiations will continue," it added.

The exact number of girls still being held is unclear, but there are multiple reports that many of the young girls have been forced to marry their captors and have also become pregnant.

Hundreds of kidnappings

Boko Haram wants to create a Muslim state in Nigeria. Towards that end they have kidnapped hundreds, if not thousands, of people. But the mass abduction of 276 schoolgirls in April 2014 brought the extremist group international attention. Dozens of the girls escaped shortly after they were captured, but until Thursday more than 200 remained missing.

Another kidnapped girl was found in May, and Buhari vowed then to free the rest of them.

Still, the girls' parents, community leaders and international rights activists had criticized the government for its failure to free the students. The abductions brought about the international #BringBackOurGirls hashtag campaign and contributed to the downfall of Buhari's predecessor, Goodluck Jonathan.

The group behind the hashtag issued a statement on Thursday, welcoming the news and saluting the security services. It also called on the "international community to continue to support our government’s effort to rescue all other abducted Nigerians, so that parents, the Chibok community, the nation, and the world can finally put an end to this nightmare once and for all."

Malam Goni Chibok, a father of one of the kidnapped girls, echoed those comments, and urged the authorities to do everything possible to free the remaining captives.

"Even if one girl is freed, we thank God," he said. "We now have hope that our children are coming back home." 

In September, Information Minister Lai Mohammed said the government had nearly secured the girls' release three times but negotiations collapsed. A Boko Haram faction posted a video showing about 50 Chibok girls and offering a new prisoner swap in August.

Nearly two years ago the group, which has since declared its loyalty to the Islamic State, controlled a patch of land about the size of Belgium But Nigerian forces, with the aid of neighboring armies, have recovered much of the territory. However, the group still launches suicide attacks in areas surrounding its base in the northeast of the country, as well as in neighboring Niger and Cameroon.

mkg/bik/kl/jm (Reuters, AFP)