An art exhibition in China by a North Korean defector has been cancelled, gallery staff said Monday, with reports saying the show had been dismantled on official orders.

Sun Mu, who slipped out of North Korea in 1998 and uses a pseudonym because of concerns for his safety, paints satirical imitations of Pyongyang's propaganda imagery.

An exhibition of his works had been due to open at the Yuan Dian gallery at the weekend, but China is nuclear-armed Pyongyang's key diplomatic backer and aid provider, even if their relationship has been strained by the antics of leader Kim Jong-Un.

"Chinese police blocked people from entering the museum," South Korea's Yonhap news agency reported, adding that officers "removed his paintings and ad banners hung around the museum".

"Some North Korean people who are believed to work at the North Korean Embassy in Beijing were witnessed at the scene," it said.

Chinese authorities maintain strict censorship controls in all media and online, with art also subject to restrictions.

On Monday a sign on the door of the modernist concrete, steel and glass structure in suburban Beijing read: "The exhibition opening has been suspended for some reasons. Thank you for your understanding."

A staff member declined to elaborate to AFP, saying that the show had been "cancelled for internal reasons" and that management were working on an alternative project.

Sun Mu, who is based in Seoul, told AFP that the exhibition was "not being held as planned".

"I need to figure out the situation first," he added. "I can't talk too much right now."

His works have reportedly fetched up to $20,000 each, but he does not allow himself to be photographed for fear that the relatives he left behind in North Korea could be targeted for retribution.

Posters for the exhibition available online show that it was to be called "Red White Blue".

Previews quoted the organisers as saying the artist would not be able to attend his own opening because of the risk that his true identity might be revealed.

The exhibition title, they said, was a reference to the colours of the flags of the six countries "at the heart of the very complicated situation of the Korean peninsula" -- North and South Korea, China, Japan, the US and Russia.The group are all participants in the Six-Party Talks process that is meant to chart a way towards North Korean denuclearisation but has been suspended since Pyongyang walked out of the forum in 2009, shortly before its second nuclear test.

No references to the show could be found on the gallery's own website on Monday.

Beijing police did not immediately respond to a request for comment by AFP. (AFP)