0300 GMT April 06, 2020
The organization said the incident occurred on Saturday when its observers’ vehicle was hit with small-arms fire near Mariinka, a town some 20 kilometers (12 miles) southwest of the volatile city of Donetsk.
Three OSCE observers along with a paramedic and a translator were visiting the area in two armored vehicles to assess damage to a gas pipeline in the region.
The mission "heard the sound of one or two shots" and saw a hole in the window of one of the vehicles.
Ertugrul Apakan, the head of the monitoring mission, described the shooting as "entirely unacceptable."
"If monitors are unable to perform their duties, there can be no security and there can be no stabilization," he added.
There were no reports of casualties.
Violence intensified in eastern Ukraine in April 2014, after Kiev deployed troops to the regions of Lugansk and Donetsk to suppress pro-Russia forces.
Ukraine’s warring sides reached a truce deal at a summit attended by the leaders of Russia, Ukraine, France, and Germany in the Belarusian capital city of Minsk on February 11 and 12 last year. The agreement introduced measures such as a ceasefire, which officially went into effect on February 15, the pullout of heavy weapons from the conflict zones, and constitutional reforms in Ukraine by the end of the year.
The shaky deal has, however, failed to eliminate the violence in the mainly Russian-speaking regions of eastern Ukraine, with both sides trading accusations of breaching the ceasefire agreement.
In a fresh attempt on Wednesday, the Ukrainian government and pro-Russia forces struck a new truce deal following talks between Russian and Ukrainian envoys in Minsk.
Over 9,000 people have lost their lives in the conflict since it broke out.