Chinese dissident artist Ai Weiwei hit out at the country's rulers Monday, branding them "ruthless" after Xi Jinping secured a historic third term as leader.

Speaking in Tokyo after China's Communist Party wrapped up its five-yearly Congress at the weekend, Ai was referring to the dramatic exit of former president Hu Jintao from the closing ceremony.

Chinese state media said the frail-looking 79-year-old had been removed from the event in Beijing because he was feeling unwell, and that he had since recovered.

But the extraordinary episode, with Xi seemingly unfazed as Hu was lifted from his chair and escorted out, prompted speculation over whether political factors were at play.

"It's very much like a fake photo of reality, because nobody moves, nobody blinks their eyes even, he is just forced out. But it shows the top central government leaders are ruthless," said Ai, who has lived in Europe since 2015.

"A big nation, 1.4 billion people, are controlled by a group of people who have no respect... really doesn't even have personal feelings, emotions, or even just friendship or to care a little bit."

The son of a poet revered by former communist leaders, 65-year-old Ai is perhaps China's best-known modern artist and helped design the famous "Bird's Nest" stadium for Beijing's 2008 Olympics.

But he fell out of favor after criticising the Chinese government, and was imprisoned for 81 days in 2011 and eventually left for Germany four years later.

Ai said Chinese leaders "don't care that much about the money issue any more, they want to reinterpret the world order".

"Not only China but also Russia, Putin also mentioned that. They don't like the way the game has been designed by the West, which has many problems too."

Xi on Sunday cemented his status as China's most powerful leader since Mao Zedong, having abolished the presidential two-term limit in 2018, paving the way for him to govern indefinitely.

"To talk about the next five years or 10 years, this is a really imperious understanding of a state," Ai said.

But a sweeping anti-corruption drive led by Xi since he became leader a decade ago has made it risky for him to step down, the artist added.

"For him this is dangerous -- that means it's dangerous for Chinese society," he said.