For nearly eight years Xiao Yuan, chief librarian at the Guangzhou Academy of Fine Arts, substituted paintings and calligraphies with his own art and sold the originals, making almost 35 million yuan (RM21.5 million), the court heard.

Works by 20th century painter Qi Baishi — whose Ode to the Motherland fetched A$15.6 million (RM43.8 million) at a Beijing auction in 2012 and is considered one of the world's highest valued artists — were among those removed by Mr Xiao.

Mr Xiao also replaced Rock and Birds by 17th century painter Zhu Da, which was valued at A$6.5 million (RM18.3 million), local media said.

The fraudster sold 125 of the paintings at auction, while another 18 in his personal collection seized by police were valued at around A$16.7 million (RM46.9 million), prosecutors said.

Xiao, 57, told the court that others were doing the same thing with his own paintings.

"During the investigation when the police showed me a picture of my copies, I realised that 10 years earlier someone had replaced it with their own copy, because their work was very poor," he said at Tuesday's hearing.

"I could see it wasn't my own work, the standard was too bad."

A spokesman at the Beijing branch of China Guardian Auctions confirmed Xiao was one of its clients, but said it was "still verifying the details related to his case".

Police have previously closed museums in China for displaying fake exhibits.

The Lucheng museum in the north-eastern province of Liaoning was closed last year after almost a third of the 8,000 items on display were discovered to be not genuine, state media said.

In 2013, a museum in the central province of Henan was found to have scores of fake exhibits, including a vase decorated with cartoon characters but described as a Qing dynasty artefact.