Lee Teng-hui, the former leader of Taiwan, addresses a forum on June 24, 2015. [Photo/IC]

BEIJING -- China on Friday voiced grave concern and strong dissatisfaction over Japan's decision to allow former Taiwan leader Lee Teng-hui to visit Japan.

"Lee Teng-hui is a stubborn Taiwan splittist," said Foreign Ministry spokesperson Lu Kang in a press release.

Despite stern representations from China, Japan assisted Lee's visit and his involvement in Taiwan separatist activities, said Lu.

The Taiwan issue concerns the core interest of China, he said, adding China is resolutely opposed to any individual trying to engage in Taiwan separatist activities in any form.

China also firmly opposes the practice of any country providing a political platform for the Taiwan splittist, he said.

We urge the Japanese side to abide by the principles enshrined in the four political documents signed by China and Japan, including the China-Japan Joint Statement, and fulfill its solemn commitments to China, said Lu.

He urged Japan to stick to the One-China policy and deal with Taiwan-related issues in a prudent and appropriate manner and refrain from creating a new political barrier for China and Japan.

Lee Teng-hui, former Taiwan leader and Kuomintang Chairman, has long been engaged in activities of "Taiwan independence". He served as the island's leader from 1988 to 2000.