Updated at 7:36 p.m. ET: LONDON -- A 26-year-old man was arrested Monday for the defacement of a Mark Rothko painting at London's leading contemporary art museum.

The incident took place on Sunday when a visitor to Tate Modern applied "a small area of black paint with a brush to the painting," to a painting titled "Black on Maroon" by the Russian-American artist.

The man arrested signed his name on the painting: Vladimir Umanets. He was placed in custody around 9 p.m. local time.

Photographs of the damage showed the text "VLADIMIR UMANETS '12, A POTENTIAL PIECE OF YELLOWISM'' scrawled on Rothko's 1958 canvas "Black on Maroon.

'Not art or anti-art'
Using a phone number posted on on the so-called "Yellowism" movement's website, a Reuters journalist spoke to a man answering to the name Vladimir Umanets who said he carried out the attack.

"I'm aware they (the police) will come at some point and arrest me,'' he told Reuters. "It was an artistic statement, but it was more about having the opportunity to speak about galleries and art."

A manifesto posted on the website reads: "Yellowism is not art or anti-art. Examples of Yellowism can look like works of art but are not works of art ... Art is forever developing 'diverse whole'. Yellowism is forever expaning 'homogeneous mass'."

Tim Wright who witnessed the incident described it as "surreal." He posted a picture on Twitter and described how "this guy calmly walked up, took out a marker pen and tagged it."

In another tweet, Wright wrote: "Very bizarre, he sat there for a while then just went for it and made a quick exit."

Amy Griffin, an art restorer at London's Simon Gillespie Studio, said she was optimistic that the painting could be repaired.

"The exact material the graffiti was done in will determine how quickly it can be removed," she said. "If it is water soluble this may be done quickly but if it has stained the original paint the conservation may take longer and some retouching might be needed."

Griffin said that while the painting wasn't on the market, the value would only be affected if the new black paint couldn't be removed.

"Removing graffiti or accidental damage to paintings done with pens, paint or even old restoration is a daily part of a conservator's job and the Tate conservation department is one of the best in the world," she said.

The damaged painting is part of Rothko's Seagram series. Originally commissioned for the Four Seasons' restaurant in New York, the artist changed his mind about the project and gave the works to galleries, including Tate Modern.

Much of Rothko's work is characterized by canvases with large rectangular blocks of color.

The last major piece by the artist to be sold was his "Orange, Red, Yellow". It  fetched $87 million at an auction in New York earlier this year.

The Tate Modern is no stranger to action by so-called artists. In 2000, two Chinese performance artists tried to relieve themselves in one of the gallery's most famous sculptures: a urinal by Marcel Duchamp.

The Metropolitan Police confirmed to NBC News that they were investigating the incident but said Monday that no arrests had been made.

Reuters contributed to this report.

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OSLO -- A Norwegian art gallery lost a Rembrandt etching worth up to $8,600 in the mail after trying to save money on courier and insurance costs, the gallery's chief said Thursday. 

The Soli Brug Gallery in Greaaker, about 50 miles south of Oslo, purchased a copy of Rembrandt's "Lieven Willemsz, van Coppenol, Writing-Master" made in around 1658, from a British dealer -- only to have it lost in the Norwegian postal system. 

"Using a courier or special insurance is quite expensive so we have used regular mail until now," Ole Derje, the gallery's chairman said. "It is worth around 40,000 to 50,000 crowns ($6,900-$8,600) and the postal service is offering us compensation of 500-1,000 crowns." 

Derje said his gallery, which is displaying works by Dürer, Rembrandt, Goya, Munch and Dali, received notice to pick up the package but when he went to collect it, it was nowhere to be found. 

Derje declined to name the seller, citing confidentiality concerns. 

"We are sorry that this has happened; we have advised him to use a more appropriate form of mail when sending items that are worth as much as this with the appropriate insurance connected," said Hilde Ebeltoft-Skaugrud, a spokesman for the postal service. 

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