Shell (SHEL.L) is suing Greenpeace for $2.1 million in damages after the environmental group's activists boarded the company's oil production vessel in transit at sea this year, according to Greenpeace and a document seen by Reuters.

The British oil and gas major filed the claim in London's High Court. Greenpeace activists boarded the vessel in January near the Canary Islands off the Atlantic coast of northern Africa to protest oil drilling and travelled on it as far as Norway.

Four Greenpeace activists used ropes to hoist themselves onto the vessel from inflatable boats that chased the ship at high speed.

Protests at sea against oil, gas or mining infrastructure have long been part of Greenpeace's operations.

The damages Shell is seeking include costs related to shipping delays and expenses for extra security, as well as legal costs, according to a document seen by Reuters.