Greenpeace activists in an inflatable speedboat said Monday they had attached themselves to the anchor of a Russian ship taking workers to the country's first Arctic oil production base.
The second raid against the Gazprom rig in three days comes as Russia takes the lead from other Arctic powers in exploiting previously untouched territory for what is believed to be one of the world's largest deposits of recoverable oil and natural gas.
Six Greenpeace International activists occupied the remote base in the southeastern section of the Barents Sea on Friday for some 15 hours before leaving after being pelted by workers with chunks of metal and hosed with ice water.
Greenpeace said its Executive Director Kumi Naidoo -- a South African who led Friday's action -- and six others raced toward the same platform at dawn Monday to intercept a passenger vessel carrying a Gazprom replacement crew.
"The activists have attached themselves to the anchor chain of the Anna Akhmatova (passenger ship) and chained their boat to it," Greenpeace said in a statement.
"The Prirazlomnaya (oil rig) has requested help from the Russian coast guards, who are on the scene, but have not yet intervened," the statement added.
There was no immediate reaction to the action from Gazprom or the Russian coast guard service.
But Greenpeace said that it had been able to send two more speedboats with seven more activists to the scene from its Arctic Sunrise icebreaker several hours after the first.
"Today we're taking peaceful action in the heart of Arctic destruction to stop this platform from wrecking these pristine waters," Naidoo said in the statement.
Russia's largest energy company is due next year to begin producing up to seven million tonnes of oil annually from the country's first field in the fragile Arctic.
The unit plans to drill and process oil before putting it onto tankers -- operations that have never been performed in such an inhospitable climate -- and is being watched closely by other energy giants planning to pursue similar work.
But critics warn that such operations are extremely risky because the base is sealed in ice for most of the year and has to work smoothly in temperatures that often plunge to minus 50 degrees Celsius (minus 58 Fahrenheit).
Naidoo tweeted several hours into the raid that the global green action network was "finishing what we started" on Friday in a bid to raise global awareness of the impending Arctic operations.
Gazprom is set to be soon joined in the Arctic by the US super-major ExxonMobil and Russia's state oil holding Rosneft -- an alliance sealed last year as part of Kremlin efforts to finally tap an area it views as the future of Russia's energy wealth.
Russia is one of the world's top two oil producers and the world's top exporter of natural gas.
But its crude production has been stalling and is soon set to decline as old Soviet era wells developed in Siberia start to slowly run dry.