The 32-year-old former nurse was among a group of 23 South Koreans captured by Taleban militants two weeks ago.

She spoke to US television network CBS last Thursday and her desperate plea for help was broadcast and reported in newspapers worldwide.

'We are in a very difficult time. Please help us. We are all pleading for you to help us get out of here as soon as possible.

'Really, we beg you,' she said in a trembling voice, between sobs. The three-minute interview, arranged by a Taleban commander, was believed to be conducted in the presence of her captors.

It is still not clear why she identified herself as Yo Cyun Ju in the interview, but back home, her family immediately recognised her voice.

'The moment I heard the voice on TV, I knew instantly that it was my younger sister,' her brother Yim Cheol told South Korean daily JoongAng Ilbo.

'My sister has already adjusted to the local environment, so she could communicate accurately,' he said.

She spoke in Korean and in the Afghan dialect of Farsi during the interview conducted late last Wednesday.

'She is in a dangerous situation, but she appeared to be calm,' Mr Yim, 34, said.

'We are at least fortunate to find out that she is alive,' he added.

His sister has been involved in humanitarian work in Afghanistan for three years, reported Korea Times.

She was acting as a guide for the church volunteers from the Saemmul Community Church (SCC) near Seoul when the group was abducted at gunpoint on July 19.

After graduating from Daegu Science College's nursing department, she worked as a nurse at Severance Hospital in Seoul.

Three years ago, she joined medical aid group All Nations' Friendship (ANF) and decided to travel to Afghanistan despite fierce opposition from her parents.

'She is the only daughter among four children. My parents initially opposed her decision to go to Afghanistan, but she had a very strong desire to go. Her determination eventually persuaded my parents,' said Mr Yim Cheol.

She left home in 2004, but not before giving her entire savings of 30 million won (S$48,000) to her parents.

The family was briefly reunited last month when she returned with two Afghans - a teenage girl who lost both arms during the war and a woman who is in her 30s and had no teeth.

With Ms Yim's help, they found sponsors in South Korea and underwent surgery at Severance. The teenager now has artificial arms.

'I hope the Taleban understand that the volunteers truly love Afghanistan,' said Mr Yim.

'It is hard to understand why these young people, who went there to help those in need, are being held hostage,' he told JoongAng.

His sister had originally planned to stay in South Korea until early September, but chose to return to Afghanistan on July 3 when she heard of the church volunteers' trip.

'She left hurriedly, saying the volunteers would have difficulty in communication without her,' the brother told Korea Times.

'I regret that I did not stop my sister.'

'I hope the Taleban understand that the volunteers truly love Afghanistan. It is hard to understand why these young people, who went there to help those in need, are being held hostage.'
MR YIM