An oil-like substance has been poured around one of the British Museum's statues by activists urging it to end its sponsorship deal with BP.
The targeted relic, Hoa Hakananai'a, is a giant carving of a human head and torso and is about 1,000 years old.
A group called Culture Beyond Oil carried out the protest. A similar protest targeted Tate Britain in June.
The British Museum said the substance involved was molasses, which had not damaged the Easter Island statue.
The Gulf of Mexico oil spill has led to campaigners stepping up their opposition to BP, with protests targeting London institutions backed by the oil company.
Culture Beyond Oil said in a statement that it had chosen the object because it "represents the way in which civilisations once considered invincible can collapse in a short period of time".
The group said the five activists who took part, their faces clad in black veils, were careful not to pour the "non-toxic" substance on the sculpture, which stands on a plinth as part of the museum's Living and Dying display.
One of the protesters said: "Institutions such as the British Museum are amongst the most valuable assets that this country has, but their worldwide reputation is being tarnished by the sponsorship deal with BP."
Last month there was a similar protest at Tate Britain, whose summer party was disrupted when an oil-like substance and feathers were thrown.
The British Museum said: "BP is one of the British Museum's most long-standing corporate partners, supporting the museum since 1996.
"We are grateful to BP for their ongoing support, which enables us to fulfil our mission of bringing world cultures to global audiences."