A South Korean Christian who taught languages to two abducted and murdered Chinese nationals at his school in Pakistan has been arrested.

Police in Pakistan also arrested members of the man's family. He is being accused of training Chinese people to do Christian missionaary work in Pakistan.

The South Korean man's school is in Quetta, southern Pakistan. He had lived in Pakistan for six years.

Li Zingyang, aged 24, and Meng Lisi, 26, were abducted and murdered by  Islamic State after it was learned they were using business visas as a cover for missionary work.

They were among about a dozen Chinese people ostensibly studying Urdu and at least one other language at his school. 

'The Korean family was training the Chinese nationals in missionary work,' said Quetta police official Abdul Razzaque Cheema told the Pakistan daily newspaper DAWN. 'We have interviewed around 50 people who were in contact with the Chinese and received text messages or calls from them. All of them have corroborated that the Chinese were involved in preaching.'.

Christian Today reported the abduction and murder of the two Chinese last  month by armed men posing as police. Islamic State's Amaq news agency reported that the men had been killed by ISIS. 

'The minister observed that it is highly unfortunate that a misuse of the terms of (the) business visa contributed to the unfortunate incident of abduction and subsequent murder of two innocent Chinese,' the ministry said then. 'Instead of engaging in any business activity, they went to Quetta and under the garb of learning (the) Urdu language from a Korean national...were actually engaged in preaching.'

The incident prompted calls for review of Pakistan's security and visa processes for Chinese nationals, and a databank that would track Chinese nationals working in Pakistan. China's foriegn ministry previously said it would cooperate with Pakistan in the investigation, and said it opposed all forms of terrorism.