The environmental group Greenpeace said one of its ships has defied Russian authorities and entered Arctic waters to protest against oil drilling, AP reported. Greenpeace says Russia this week denied permission for its Arctic Sunrise ship to enter the Kara Sea, a section of the Arctic Ocean off Siberia. But the ship entered the waters on Saturday morning, Greenpeace said in a statement. The group is protesting offshore oil exploration adjacent to Russia's Arctic National Park, which is habitat for polar bears, walrus and other animals. The exploration is being conducted by state oil company Rosneft and ExxonMobil. Greenpeace campaigner Christy Ferguson said in a statement that if the companies bring in oil drilling platforms, there's a risk of oil blowouts and spills that could severely damage the park.