New evidence has surfaced about the abduction and reported murder of two Chinese nationals by the militant Islamic State (IS) group in Quetta, the interior ministry said on Friday.

The ministry has cancelled the visa of a South Korean national who it had earlier linked to the abduction incident.

The interior minister was earlier told that the Chinese couple had gone to Quetta and were engaged in preaching under the garb of learning Urdu from a Korean national, Juan Won Seo, who is the owner of ARK Info Tech.

It was revealed during the investigation, the ministry said on Friday, that South Korea Juan Won Seo alias Gilbert came to Pakistan on a business visa but set up an Urdu academy and was "engaged in illegal activities".

It also emerged during the investigation that the two Chinese nationals had been taken into police custody from Quetta's Kharotabad area some time ago and were informed about threat to their security.

"They were offered security but they refused to accept the offer," the ministry said.

Security and intelligence agencies are closely looking into the background of the incident and reviewing photos of the kidnapped pair released on social media so they could reach some conclusion and it could also be confirmed whether the Chinese nationals were actually killed or not, the statement said, quoting ministry sources.

China's Foreign Ministry on Tuesday said it would work with Pakistani authorities to investigate reports the two Chinese nationals were missionaries.

The pair, identified by authorities as Lee Zing Yang, 24, and Meng Li Si, 26, were abducted by armed men pretending to be policemen on May 24 in Quetta. Last week, IS' Amaq propaganda agency claimed its members had killed them.

The kidnapping was a rare crime against Chinese nationals in Pakistan but it has alarmed the growing Chinese community in the country.

The interior ministry on Monday alleged for the first time that the two were preachers who had abused the visa system by posing as business people to enter the country.

“Instead of engaging in any business activity they went to Quetta and under the garb of learning Urdu language from a Korean national... were actually engaged in preaching,” the ministry said in a statement.