Japan-born pandas Xiao Xiao and Lei Lei arrive home in China's Sichuan

China's giant pandas Xiao Xiao and Lei Lei have arrived safely in Sichuan on Wednesday, China's panda research base said in a social media post, following an emotional goodbye from fans in Tokyo where the pair were born and raised.

Xiao Xiao and Lei Lei arrived at Chengdu's Tianfu International Airport on 1 am on Wednesday, a WeChat post by the China Conservation and Research Centre for the Giant Panda showed.

They reached the centre in Ya'an, Sichuan, panda diplomacy to boost its international image and cement ties with other countries by gifting or loaning out pandas.

The pandas typically return home after the agreement ends, and pandas born overseas like Xiao Xiao and Lei Lei usually go to a Chinese breeding program between the age of two and four.

Pictures on the WeChat post showed the pandas' crates being unloaded from a Sichuan Airlines plane and then transported to a truck while workers in white protective suits look on.

Xiao Xiao and Lei Lei have "continuously put up bridges of friendship between the people of China and Japan" and "made a positive contribution to promoting friendship between the peoples of the two countries", the research centre said.

The panda's journey coincided with a low point in Sino-Japanese relations. In November, Japanese Prime Minister Sanae Takaichi said Japan would respond militarily in the event of a Chinese attack on democratically governed Taiwan.

China, which regards Taiwan as a wayward province, reacted angrily to the comment and advised citizens against travelling to Japan.