China said on Friday it is "gravely concerned" at reports that two of its nationals kidnapped in Quetta last month have been killed by their captors.

The Chinese Foreign Ministry made the statement after reports surfaced that Daesh had claimed responsibility for the kidnapping and killing of the Chinese nationals.

Two foreign nationals kidnapped from Quetta

The husband and wife were working at a Korean language centre since the last year

However, the reports have not been confirmed by Pakistani officials in the provincial or the federal government.

Armed men pretending to be policemen kidnapped two Chinese language teachers ? a man and a woman ? in Quetta?s Jinnah Town on May 24.

Following the incident, a case was registered and a three-member investigation team headed by Balochistan Counter-Terrorism Department DIG and including the SSP Investigation and SP Saddar was formed to probe the case.

"We have been trying to rescue the two kidnapped hostages over the past days. The Chinese side is working to learn about and verify relevant information through various channels, including working with Pakistani authorities," said Chinese Foreign Ministry Spokesperson Hua Chunying in a short statement on June 9.

"The Chinese side is firmly opposed to the acts of kidnapping civilians in any form, as well as terrorism and extreme violence in any form," it said further.

On Thursday, the Pakistan Army said it had killed 12 terrorists working to establish contact with Daesh in an operation in Balochistan?s Mastung area on the weekend of June 2.