Kurdish forces in northern Iraq who are fighting Islamic State (IS) militants were attacked with chemical weapons a few days ago, the German defence ministry said on Thursday.
"There was a chemical weapons attack" southwest of Arbil, a ministry spokesman told AFP, adding that some Kurdish fighters suffered respiratory problems while German military trainers were unhurt.
The chemical agent had been delivered with mortar or artillery shells, said the spokesman, who did not say who was suspected of carrying out the attack.
"American and Iraqi specialists from Baghdad are on their way to find out what happened," he added.
Germany has been supporting the Kurdish peshmerga fighters with arms shipments and weapons training since September to back the fight against IS jihadists, and currently has about 90 personnel on the ground.
"German soldiers were not affected or in danger," the spokesman said. "The protection of our soldiers in northern Iraq is already at the highest level."
IS has previously been accused of using chlorine against Kurdish forces in Iraq.
In March, the autonomous Kurdish government in northern Iraq said it had evidence that the jihadist group used chlorine in a car bomb attack on January 23.
Last month, the Conflict Armament Research group and Sahan Research group said IS had also targeted peshmerga with a projectile filled with an unknown chemical agent on June 21 or 22.
The chemical used had characteristics and clinical effects "consistent with a chlorine chemical agent," the groups said.
The organisations said they had also documented two such attacks against Kurdish fighters from the People's Protection Units in Syria's northeastern Hasakeh province on June 28.
It said that upon impact, the projectiles had released a yellow gas "with a strong smell of rotten onions".
There were no deaths but troops exposed to it had experienced burning of the throat, eyes and nose, severe headaches, muscle pain, impaired concentration and mobility, and vomiting.