Dark, bare photos of modern Chinese society by Liu Xia, detained wife of China's best known dissident, went on show in New York without her knowledge after they were spirited out of her country.

The photos were brought out of China under the noses of the authorities by French academic, writer and economist Guy Sorman, a friend of the artist and her Nobel Peace prize-winning husband Liu Xiaobo.

Liu Xia, who is under house arrest in Beijing while her husband serves an 11-year jail term for propagating democracy, made it a condition of the deal that the exhibitions were kept a secret from her, Sorman said.

"She does not know. She does not want to know," Sorman told AFP ahead of the the opening on Thursday of the exhibition he curated.

"She gave me permission to show them. But she did not want to know where or when. As she is a woman who would never lie, if she is questioned by police she can say that she does not know, and she really doesn't know."

The 25 photos in "The Silent Strength of Liu Xia" will be displayed at Columbia University in New York until March 1 before going to Madrid and what could be a politically-charged exhibition in Hong Kong later in the year.

They were shown at Boulogne-Billancourt, just outside of Paris, last year.

Sorman has known the Liu family for 15 years but only convinced Liu Xia to display her work just before she was put under house arrest in 2010.

Convincing her was more difficult than getting the images -- in which dolls are used to show the suffering of the Chinese people -- out of the strictly policed country, Sorman said.

"It was a bit complicated, I am not going to say how. I would just say that it was not illegal," he said.

Though Liu Xia has been restricted to her home for more than a year, she has never been charged with any illegal act.

"When the exhibition was held in France, the Chinese ambassador protested -- half-heartedly because he knew he had no grounds to protest," Sorman said.

Sorman, who now communicates only with the artist's mother, said the photos were taken out of China individually.

"It took me several months to persuade a number of people. Each one carried one photo. If we had taken them out together it would probably have been difficult. The whole thing took a year," he said.

Liu Xia could never stage an exhibition in China because she is the wife of the country's best known dissident. Sorman insists, however, that she is not involved in political activities.

"Artists are always dissidents," said Sorman. "But Liu Xia is an artist and I am presenting her here as an artist."

The French academic stresses that the world is now discovering an "important" Chinese artist.

"This is no an anti-Chinese exhibition. On the contrary, this shows that there is a renaissance of Chinese culture, following modern forms of expression. This is not folk art."

The black and white images show dolls in different positions in the Liu family's apartment in Beijing -- one shows a pained Liu Xiaobo holding a doll on his shoulder. Another doll is tied up, and another is wrapped in plastic.

Many show tears. All present a grim outlook.

"They represent an aspect of Chinese society which we don't speak a lot about. The Chinese propaganda machine always shows a celebration of Chinese successes," Sorman said.

"With this exhibition, you can see there is also oppression, poverty, distress, darkness. It is impossible to express yourself."

"So there are two messages: one, that there is a cultural renaissance, but secondly, the suffocating society. A society which cannot breathe."

Sorman said Hong Kong's PEN Club is scheduled to show the pictures in the Chinese territory at the end of April as part of a tribute to the Lius.

"This will be artistic because it will be in a museum. I insist on this. But there will clearly be a stronger political dimension in Hong Kong."