A pair of crested ibises from China arrived in Japan on Wednesday as a symbol of friendship, for the first time since 2007, amid warming relations between the two countries.

The donation by China of the internationally protected species came as this year marks the 40th anniversary of the two countries signing a bilateral peace and friendship treaty and ahead of Prime Minister Shinzo Abe's official visit to Beijing next week.

After arriving at Narita airport near Tokyo, the birds were transferred to the Sado Japanese Crested Ibis Conservation Center in Niigata Prefecture in the evening.

The 2-year-old male and female ibises, named Lou Lou and Guan Guan, respectively, were born and raised in China's northern province of Shanxi, according to the Environment Ministry.

Japanese-born ibises became extinct in 2003. Since then, Japan has been artificially breeding ibises by relying on the Chinese donations, the first of which was in 1999, and preparing them for reintroduction into the wild.

Since 2008, Japan has been releasing the ibises on Sado Island and their number is now estimated to be over 350.

During his visit to Tokyo in May, Chinese Premier Li Keqiang agreed on China's first provision of the endangered birds to Japan since November 2007.

In 2011, then Chinese Premier Wen Jiabao expressed Beijing's intention to offer ibises to Japan, but the plan was shelved after a diplomatic dispute escalated in the wake of the Japanese government's decision a year later to put the Senkaku Islands in the East China Sea under state control.

Although China continues to claim the uninhabited islands, which it calls Diaoyu, ties between Tokyo and Beijing are currently much better than they used to be several years ago.