A separatist leader made the accusation at a joint news conference in the rebel-controlled city of Lugansk with Alexander Hug -- the principal deputy chief of the group's special monitoring mission to Ukraine --- who denied the claim.
The OSCE is a Cold-war era body drawn up to ensure peace in Europe. Its main role in the Ukrainian conflict is to report ceasefire violations and organise periodic peace talks.
Alexander Zakharchenko of the self-declared Donetsk People's Republic voiced suspicions that the OSCE was handing government troops the locations of civilian infrastructure that comes under fire.
"As soon as we give you the coordinates of our facilities, by a strange coincidence those very facilities come under attack," he said alongside Igor Plotnitsky, the head of the self-declared Lugansk People's Republic.
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"Our towns and our infrastructure -- electricity pylons and water towers, schools and hospitals -- come under attack," Zakharchenko said.
"This leaves us somewhat bewildered. How does the Ukrainian army get these coordinates?" Zakharchenko asked.
Plotnitsky also came out with sharp accusations.
"When I watched the Ukrainian forces attack you, how you yourself came under attack, somewhere in my soul a tiny hope flickered that one day, you would begin to tell the truth," he said, addressing Hug.
The OSCE has been a neutral observer throughout one of Europe's bloodiest crises since the 1990s Balkans Wars. It issues daily reports about truce breaches by both sides.
The OSCE has around 600 monitors who risk their lives in the war zone that borders Russia, and another 100 across Ukraine.
More than 10,000 people have been killed and around two million driven from their homes since the war began in April 2014.
Ukraine has called for the monitors to be armed to turn them into a peacekeeping mission along the lines of the United Nations' blue helmets.