The incident comes at a sensitive time with Turkey in talks to end the conflict with the Kurds after the PKK militant group agreed to end its decades-long armed struggle.

The conflict, which began in 1984, has cost more than 40,000 lives.

The incident occurred as they were searching for the remains of a soldier who was shot dead by Kurdish fighters in the area in May 2022, whose body was never recovered, it said.

At the time, Turkey was waging Operation Claw Lock, with its troops seeking to eradicate Kurdish PKK militants holed up in caves along the border.

"During a search operation in a cave... previously known to have been used as a hospital... 19 of our personnel were exposed to methane gas." it said.

They were immediately taken to hospital for treatment, but five of them died, it said.

News of the deaths emerged as a delegation from the pro-Kurdish DEM party was visiting jailed PKK founder Abdullah Ocalan as part of the ongoing negotiations with the Turkish government.

"During the meeting, we were informed that there were soldiers who lost their lives due to methane gas poisoning in the territory of the Kurdistan Regional Government," the delegation said.

"This incident caused Mr Ocalan and all of us deep sadness. We wish Allah's mercy to those who lost their lives and offer our condolences to their families and relatives."