Isis on Thursday (8 June) claimed it kidnapped and killed two Chinese nationals from Pakistan's southwestern Balochistan province about two weeks ago, according to the group's Amaq news agency.
The Chinese nationals were reportedly kidnapped by armed men disguised as police on 24 May from the provincial capital of Quetta, where the duo are believed to have been studying Urdu at a language centre.
"Islamic State fighters killed two Chinese people they had been holding in Baluchistan province, southwest Pakistan," the news agency said in an Arabic statement on the Telegram messaging app on Thursday.
Authorities in Baluchistan and China said they were verifying the claims, with the Chinese foreign ministry expressing "grave concern" over the report.
"We have been trying to rescue the two kidnapped hostages over the past days," the Chinese ministry said in a short statement and added that they were "working to learn about and verify relevant information through various channels, including working with Pakistani authorities".
The ministry also stated that their country is "firmly opposed" to violent acts of terrorism.
Local media reports also stated that another Chinese woman, who was present at the time of the abduction, managed to flee, the BBC wrote.
Isis has created its presence in Afghanistan and is reported to be struggling to spread across neighbouring Pakistan. The jihadist group has claimed several attacks in the two nations, including Balochistan, but this was the first incident where foreign nationals were targeted.
China and Pakistan are close allies and the two are currently involved in strengthening economic ties through a One Belt Road initiative.
Pakistan has so far made no comments on the incident, but has previously been facing huge pressure from the US on tackling home-grown terrorism.