By Wednesday evening, Russian investigators had formally charged at least 14 of the Greenpeace activists, with charges pending against some 16 others.
Earlier in the day, two activists from the same were the first be formally charged with piracy over an open-sea protest against Arctic oil drilling, an activist said.
"The first two activists have been charged with piracy," Mikhail Kreindlin, a representative of Greenpeace, told the AFP news agency. "These activists are from Brazil and Britain."
The charge is punishable by up to 15 years in prison.
The two charged were among 30 activists arrested by Russian authorities last month when they tried to board an oil platform operated by the state concern Gazprom in the Pechora Sea.
Two activists who tried to scale the platform but eventually slipped into the freezing water were recovered by the Russian coast guard. Agents from Russia's Federal Security Service (FSB) then seized the Greenpeace ship, the Arctic Sunrise.
Rising average temperatures in the Arctic attributed to climate change and opening up of sea lanes have prompted energy producers to seek access to oil and gas reserves.
Greenpeace argues that oil spills and lack of precautions pose severe dangers to icy regions that are home to polar bears, walruses and rare seabirds.
hc/mkg (Reuters, AFP)