The governor of Nigeria's Niger state held a ceremony on Monday to welcome back 130 kidnapped children and teachers released after a month in captivity.

Their kidnapping from a Catholic boarding school in Niger state's Papiri community was one of the worst mass abductions in Nigeria’s history. No one has claimed responsibility, but local residents blame armed groups looking for ransom.

School kidnappings have come to define insecurity in Africa’s most populous country. Now, authorities say they are stepping up security.

"We are implementing immediate short-term protective measures in high-risk areas, while concurrently working with state governments, traditional and religious leaders, to develop lasting community-based security solutions for education," Adamu Laka, a national coordinator with Nigeria's Counter-Terrorism Centre, said on Monday.

"It must not be a casualty of violence. We will continue to pursue policies and operations to restore confidence, reopen schools safely, and ensure that the right of every Nigerian child to learn in safety is upheld."

Officials ducked questions about whether ransoms were paid to secure their release.

"I don't think it's very fair to the system, to the government, for you to ask whether money was used or not. The most important thing we have gotten these people back unhurt," Niger State Governor, Mohammed Umar Bago told reporters on Monday. "The other one is for us, not for you. So, I think the most important thing is that we have recovered missing children, and how we did it, we know it.”

Most of the kidnapped children were aged between 10 and 17, their school said. They’re scheduled to be reunited with their families before Christmas.