Greenpeace activists board Shell North Sea platforms

Greenpeace campaigners have boarded two Royal Dutch Shell oil platforms in a protest against leaving parts of old rigs in the North Sea, the environmental group said Monday.

The campaign group said in a statement that activists have scaled Shell's Brent Alpha and Bravo platforms, which lie northeast of Scotland's Shetland Islands and are no longer operational.

Climbers from Denmark, Germany and the Netherlands unfurled banners saying: "Shell, clean up your mess!" and "Stop Ocean Pollution", according to photos issued by Greenpeace.

The campaign group claimed that Shell's decommissioning plans would leave portions of four Brent oil platforms at sea with some 640,000 cubic metres of oily water and 40,000 cubic metres of oily sediment, containing an estimated 11,000 tonnes of oil.

"Shell's plans are a scandal and go against international agreements to protect the environment," said Greenpeace campaigner Christian Bussau.

"With escalating climate emergency, biodiversity loss and species extinction, we need healthy oceans more than ever."

However, Shell responded in a statement received by AFP that said it has spent ten years conducting in-depth research into decommissioning the Brent platforms -- and added that its recommendations were the result of more than 300 scientific and technical studies.

"We can confirm that two protestors have boarded the Brent Alpha platform and one has climbed onto the Brent Bravo concrete legs," a Shell spokesman said.

"Their safety and that of our workers are our prime concern at this moment."

He added: "Our proposals were submitted only when we were convinced they were the best option: safe, environmentally sound, technically achievable, and socially responsible."

Separately on Monday, Extinction Rebellion campaigners blocked a junction outside the Bank of England in the heart of London's City finance district.

The protesters claim trillions of pounds (dollars, euros) are pumped through London's financial markets investing in fossil fuels that damage the climate.

London's Metropolitan Police have moved to try to minimise wide-scale disruption in the British capital since the start of a two-week Extinction Rebellion protest which began last week.