At least 137 of 286 Nigerian children kidnapped more than two weeks ago from a school were reportedly rescued on Sunday.

Nigerian military officials said 76 females and 61 males were rescued in the state of Zamfara, Reuters reported. An initial statement claimed that all of the children were freed but that number was later lowered.

"Efforts would continue until other hostages are found and the terrorists arrested, tried, and brought to justice by Nigerian law," Nigerian military spokesman Maj. Gen. Edward Buba said in a statement obtained by the Associated Press.

Gunmen had demanded 1 billion nairas, the equivalent of about $620,432, for the release of the victims, according to a spokesman and local councilor for the families.

Students and members of the school staff were abducted on March 7 in the town of Kuriga, in Nigeria's northwestern Kaduna State. At least 100 of the abductees were aged 12 or younger.

According to witnesses, the pupils were in the assembly ground at the school when dozens of gunmen rode up on motorcycles and marched the students away.

One student died after being shot by the gunmen, the BBC reported.

Kaduna state Gov. Uba Sani, who first announced the rescue, did not give details on how they were freed.

In a statement, he said, "The Nigerian Army also deserves special commendation for showing that with courage, determination and commitment, criminal elements can be degraded and security restored in our communities."

Kidnapping gangs have seized thousands of people in Nigeria in recent years.

Arrests are rare in the mass kidnappings, according to the Associated Press, as victims are usually released only after families pay ransoms.