Nigerian security forces have rescued eight students and three teachers who were from among some 100 people abducted last Friday from a school in northwest Kebbi state.

Nigerian authorities on Sunday said the kidnappers killed three of the students and they are looking for those still believed to be held captive for ransom. Five students and two teachers were rescued in a joint army and air force operation on Friday, a few hours after their abduction.

Later on, three students and another teacher were freed. Troops, however, also recovered the bodies of the dead students. Two of them had been shot in the legs while one was believed to have died of exhaustion. Kebbi state official Yusuf Sununu told a Lagos TV station that security forces are making progress with the rescue mission.

"The military are there and the bandits have suffered so many casualties. And the way things are going, we do hope with the efforts of the military that camp will be completely done away with," said Sununu.

Last week, some 94 students and eight teachers were abducted in broad daylight from the government school in Birnin Yauri, in northwest Kebbi state. The attack was the latest in Nigeria's rising trend of school kidnappings for ransom. It occurred barely two weeks after more than 130 young pupils of an Islamic seminary were taken from the nearby central state of Niger.

The Nigerian military said in a statement Sunday that it killed one of the kidnappers during an exchange of gunfire and deployed more troops to search forest hideouts. Over the weekend, local hunters in Kebbi met with the state governor and pledged to join the search for the remaining abductees.

But Amnesty International's Seun Bakare says the repercussions of increasing school attacks are huge.

"The recent abductions we have seen across different states in northern Nigeria tell us that the government is either unwilling or unable to secure schools and protect the right to education. Millions of children are now having to pay the price of government's failure to protect citizens from violence," Bakare said.

In reaction to the kidnappings, hundreds of schools in the north have shut down, according to Amnesty.

The government has moved to outlaw the paying of ransom, and earlier this month President Muhammadu Buhari said he had ordered security agents to be "ruthless" in tracking down the kidnappers.