Moscow - Greenpeace activists in an inflatable speedboat said on 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 that 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.

Russia's largest energy company is due to begin producing up to seven million tons 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 drilling.

But critics warn that the work is extremely risky because the platform is sealed in ice for most of the year and has to work smoothly in temperatures that often plunge to minus 50 degrees Celsius.

Naidoo tweeted several hours into the operation that Greenpeace was “finishing what we started” on Friday in a bid to raise global awareness of the impending Arctic operations. - Sapa-AFP