Nineteen of the staff exposed to the gas immediately went to the hospital. By Monday, 12 of the soldiers had died, and the conditions of the others were not immediately known.
The president, Recep Tayyip Erdoğan, in a statement, conveyed his "profound sorrow" over the incident and his condolences to the families of killed servicemen and the Turkish Armed Forces.
37 Lethal Gas Levels in Cave Are Questioned
Methane gas is not poisonous in small amounts, but it can kill if large amounts are released in a confined space, as it can displace the oxygen in the air. It is not known what might have led to the cave having such a high methane level, which was apparently enough to kill.
A farewell ceremony for some of the soldiers was held on Monday at an airport in the southern Hakkari province, with the Turkish Defence Minister and the military's top brass attending. The soldiers' bodies were later sent back to their home towns for burial.
The mission that resulted in the exposure was said to be part of an attempt to retrieve the body of a soldier killed in a gunfight in the framework of Operation Claw Lock in May 2022.
Background on Operation Claw Lock and the PKK Fight
Operation Claw Lock is one of a series of military actions Turkey is conducting against the PKK, which is proscribed as a terrorist organisation by Turkey, the EU, the UK and the US. The operation consists of both airstrikes and ground incursions, and is reportedly focusing on caves and mountainous areas suspected to be used by militants.
The PKK has been fighting a four-decade insurgency in Turkey. The group originally sought an independent state; it now advocates more rights for Turkey's Kurdish minority. The fighting has killed more than 40,000 people since the 1980s.
There have been some signs in recent months that tensions could potentially ease. The PKK declared a ceasefire in March and committed to disbanding in May, saying it had "fulfilled its historical mission". As part of this transition, the group said some of its fighters would start handing over their weapons in Iraqi Kurdistan this week.
Nevertheless, Sunday's devastating event drives home the real danger for soldiers, in what they themselves say is a "risky business" - of carrying out such high-stakes operations.
