One of the missing Chibok girls has been found in Nigeria, activists say, the first to be rescued since their capture two years ago.

In all, 218 girls remain missing after their abduction from a secondary school in north-east Nigeria in April 2014.

Activists told the BBC that Amina Ali Nkek was found by a vigilante group on Tuesday in the Sambisa Forest, close to the border with Cameroon.

The girls were taken by militants from the Boko Haram Islamist group.

Amina was reportedly identified by a civilian fighter who recognised her. The fighter belonged to the Civilian Joint Task Force (JTF), a vigilante group set up to help fight Boko Haram.

News of the rescue was confirmed to the BBC by Nigerian university teacher and women's activist Hauwa Abdu.

Sources told the BBC she came from the town of Mbalala, south of Chibok, from where 25 of the kidnapped girls came. A neighbour in Mbalala told the BBC that Amina was found with a baby.

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An uncle, YaKubu Nkeki, told Associated Press news agency that Amina was later reunited with her mother in Chibok.

She is expected to be moved soon to Maiduguri, the capital of Nigeria's Borno state.

In recent days, Nigerian media reported that the army had launched a number of operations against Boko Haram in the Sambisa Forest.

Nigeria's military has not yet commented on the latest raid.

The Bring Back Our Girls campaigners and relatives of the girls have marched in Abuja to demand more be done to rescue them. Photo: AFP

During the 2014 attack, the gunmen arrived in Chibok late at night, then raided the school dormitories and loaded 276 girls on to trucks.

Some managed to escape within hours of their kidnapping, mostly by jumping off the lorries and running off into the bushes.

In total, 219 girls remained missing before the first rescue.

A video broadcast by CNN in April 2016 appeared to show some of the kidnapped schoolgirls alive.

Fifteen girls in black robes were pictured. They said they were being treated well but wanted to be with their families.

The video was allegedly shot on Christmas Day 2015 and some of the girls were identified by their parents.

The Chibok schoolgirls, many of whom are Christian, had previously not been seen since May 2014, when Boko Haram released a video of around 130 of them gathered together reciting the Koran.

The abduction led to the #BringBackOurGirls campaign, that was supported by US First Lady Michelle Obama and Pakistani activist Malala Yousafzai.

Boko Haram at a glance:

--Founded in 2002, initially focused on opposing Western-style education - Boko      Haram means "Western education is forbidden" in the Hausa language

--Launched military operations in 2009

--Thousands killed, mostly in north-eastern Nigeria, hundreds abducted, including at least 200 schoolgirls

--Joined so-called Islamic State, now calls itself IS's "West African province"

--Seized large area in north-east, where it declared caliphate

--Regional force has retaken most territory last year