London's Tate Modern was temporarily closed on Sunday after a mural by US modern artist Mark Rothko was defaced by black paint, the gallery said.
The gallery shut for a short time at around 3.25pm (1425 GMT) after the damage was found on the corner of one of the Rothko's Seagram murals.
"Tate can confirm that there was an incident in which a visitor defaced one of Rothko's Seagram murals by applying a small area of black paint with a brush to the painting," said a spokeswoman for the popular gallery.
The Seagram murals, commissioned by New York's Four Seasons restaurant in 1958, arrived in London for display at Tate Modern's sister gallery on February 25, 1970 -- the day the artist committed suicide aged 66.
A large-scale painting by the artist fetched $86.9 million at a New York auction in May, setting a new record for any contemporary work of art.
The Russian-born expressionist painter became a giant of the modern art world through his simplified and colourful compositions inspired by mythology and primitive art.
