A second Chibok schoolgirl abducted by Boko Haram more than two years ago has been found during military operations in northeast Nigeria, the army said yesterday.

Army spokesman Colonel Sani Usman said she was among 97 women and children rescued by troops and civilian vigilantes in the Damboa area of Borno state at about 11:00 am (1000 GMT).

"We are glad to state that among those rescued is a girl believed to be one of the Chibok Government (Girls) Secondary School girls that were abducted on 14th April 2014 by the Boko Haram terrorists," he added.

"Her name is Miss Serah Luka," he added in a statement.

The student, who is believed to be a Christian pastor's daughter, said she was "at the school at the time they were abducted" and that she was from Madagali, in neighbouring Adamawa state, Usman said.

This handout picture taken in Damboa and released by the Nigerian army on May 20, 2016 shows Serah Luka after she was released during an operation conducted by Nigeria’s army in which local civilian vigilantes took part. Photo: AFP

Luka said she had only been at the school in Chibok for just over two months when the kidnapping happened, he added.

Many of the 276 girls who were initially abducted were from the surrounding area and were sitting exams in Chibok as their schools were closed because of the conflict.

Fifty-seven escaped in the immediate aftermath and until this week, there had been few indications about the whereabouts of the 219 others held or their possible release.

Usman added: "She is presently receiving medical attention at the medical facility of Abogo Largema Cantonment, Biu, Borno State."

The first of the abducted students to be found, Amina Ali, was discovered by troops and civilian vigilantes near Boko Haram's stronghold in the Sambisa Forest area of Borno state, northeast Nigeria.

The 19-year-old and her mother met President Muhammadu Buhari at his official residence in Abuja earlier Thursday, where the head of state said the government was "doing all it can to rescue the remaining Chibok girls".

"Amina's rescue gives us new hope, and offers a unique opportunity for vital information," he said in a statement.

Amina was quoted as saying by a campaign group pushing for the girls' release that all the students were still being held in the former game reserve, where the Islamists have had camps, but that six had died.

Nigeria's military has been mounting an offensive in the sprawling, semi-desert scrubland since late April to flush out rebel fighters.