Ertugrul Apakan / Photo from UNIAN

"Chief monitor says those in control in DPR must stop attacks on OSCE monitors," she tweeted, with reference to a briefing of Apakan before the OSCE Permanent Council meeting in Vienna on Wednesday.

"EU in OSCE strongly condemns all restrictions, threats and attacks on OSCE SMM. This endangers crucial role of SMM in Eastern Ukraine," Plesner said.

"Jamming of OSCE UAVs in Eastern Ukraine more aggressive than ever, says chief monitor," she wrote.