CANBERRA, June 14 (Xinhua) -- A bark painting of an ancient saltwater crocodile is the showpiece of a 150-piece "Old Masters" art exhibition to tour China next month, local media reported on Thursday.

The 1965 work, featuring a mystic creature known as a totemic crocodile, was created by Yirawala, one of these old masters and an Aboriginal tribal leader who promoted and protected his heritage in Australia's western Arnhem Land, in the Northern Territory.

The 20-month tour will open in July at Beijing's National Museum of China before moving to Shanghai, Chengdu and Shenzhen.

The Australian embassy in Beijing described the tour as an "important cultural diplomacy milestone," while Dr Mathew Trinca, director of the National Museum of Australia, said it was "deeply affirming" to see growing interest abroad in Indigenous art and stories.

"I think these are some of the greatest treasures of our nation," he told national broadcaster, the Australian Broadcasting Corporation (ABC).

"They are the works that speak of the long human history of this continent from a very special part of Australia."

Dr Trinca said he was taken aback by the sense of anticipation in China at seeing these works.

"We're very focused on the idea that we need to communicate Australian stories abroad... it's an important part of the mission of the National Museum of Australia to be taking stories like these overseas," he said.

The historic journey to China marks the first time most of these artworks have left the country, and has presented the museum with several logistical challenges.

Bark is susceptible to bending and cracking in changing temperatures, so transporting the collection - including carvings and tools - from its home in Canberra to China comes with risks.

To minimize the risks, the decades-old works have been carefully restored and packed in a specially made box to prevent movement in transit.

To further stabilize each bark, the museum's conservation team has used funori, a glue made from a Japanese seaweed extract used to preserve kimonos.

In preparing for the tour, the museum has consulted Arnhem Land art centers and relatives of the late artists to add more details to the stories the barks display.