The Organization for Security and Cooperation in Europe (OSCE) says members of its monitoring mission in eastern Ukraine have been threatened at gunpoint near a village in the Donetsk region.
The OSCE said a Special Monitoring Mission (SMM) was stopped by two armed separatists near the separatist-controlled village of Lukove in the afternoon on July 29.
This occurred, the OSCE said, while the SMM was following what it said were fresh tracks, likely left by an infantry fighting vehicle.
The separatists blocked the road with their camouflaged-style jeep and pointed their guns at the monitors and ordered them to leave the area, according to the OSCE.
As the group of monitors was leaving the area, another separatist jeep appeared, traveling at top speed. It almost hit the lead vehicle in the SMM convoy before coming to a stop in front of the patrol, blocking its path.
The OSCE said one separatist made a "cut throat" sign to the monitors and took photographs of both SMM vehicles and the drivers.
The OSCE monitors were led to a separatist checkpoint in Prymorske, some five kilometers south of Lukove.
There, according to the OSCE, nine armed separatists surrounded the first SMM vehicle, swearing and making threatening gestures. One of the monitor's vehicles was dented after a separatist hit it several times with his rifle butt.
The monitors were eventually released and returned safely to their base in Mariupol.
Among those condemning the separatists' actions was Liselotte Plesner, an OSCE ambassador from Denmark.
The OSCE, which includes nations from North America to Europe to Central Asia, is tasked with monitoring the shaky cease-fire in eastern Ukraine's Donetsk and Luhansk regions, where pro-Russian separatists and Ukrainian government forces still engage in regular clashes.
The organization's daily reports on cease-fire violations are of great importance to Western leaders, many of whom say they will not consider lifting sanctions against Russia until the Minsk peace deal that Kyiv and Moscow agreed to is fully implemented.
Russia has long distrusted the OSCE, accusing it of bias. The organization's special monitoring mission includes observers from more than 45 countries, including Russia, as well as 305 Ukrainian staff.