China and Pakistan said they are investigating the Islamic State group’s claim that two Chinese teachers kidnapped in Pakistan have been killed.

Chinese Foreign Ministry spokeswoman Hua Chunying told the official Xinhua News Agency on Friday that the government was seeking information from Pakistani authorities. In Islamabad, two Pakistani security officials said they were investigating but that no bodies have been found.

The IS claim came hours after Pakistan’s military released the pictures of what it said were 12 slain members of the militant group. They were killed in this week’s operation in the southwestern province of Baluchistan, where the military said it foiled an attempt to set up an organized IS militant base.

“We have taken note of relevant reports and we express our grave concern. We have been trying to rescue the two kidnapped hostages over the past days,” Ms. Hua was quoted as saying.

The two teachers at a private language school were kidnapped May 24 by gunmen dressed as police who stopped their car in Quetta, the capital of Baluchistan. A bystander who attempted to intervene was shot and wounded while rescuing a third person.

A statement late Thursday from the IS news agency said the two Chinese teachers had been killed.

Thousands of Chinese work in Pakistan and have sometimes been targeted by militants. China is a longtime ally of Pakistan and is building roads and power plants under multibillion-dollar project termed the China-Pakistan Economic Corridor.

Islamic militants opposed to Chinese rule in the northwestern region of Xinjiang are also believed to be sheltering in Pakistan’s lawless tribal areas, from which they have threatened to launch attacks.