Executive Director of Greenpeace International Kumi Naidoo and four other activists occupied the base of the Prirazlomnoye oil rig in the Pechora Sea last week. They abandoned the rig Friday after getting doused with ice water and metal thrown by the rig's crew.
The group said Monday that two high-speed boats intercepted a supply vessel that was delivering workers to the platform.
"It's not moving anywhere and so the platform workers can't get on-board, effectively stopping its preparations to drill for oil in the arctic," claimed Greenpeace.
Groups like Greenpeace say they worry about the potential effects of a major oil spill during oil and natural gas exploration in arctic waters. Russian energy company Gazprom said it paid "special attention" to safety issues when designing the ice-resistant oil platform.
Gazprom estimated reserves at the Prirazlomnoye oil field at around 527 million barrels. The Moscow Times reports operations at the rig weren't disrupted by the actions of Greenpeace.
Naidoo was arrested last year by Dutch authorities and banned from the Netherlands for one year for similar actions against Cairn Energy. A Dutch court ruled against Greenpeace after Cairn Energy sued the group.