J-League boss Mitsuru Murai promised swift action after a video showing a fan waving a banana at Kawasaki Frontale's Brazilian striker Renato lit up social media on Saturday.

"We want a quick decision," Murai told reporters. "The standard was set in 2010," he added, referring to a 5 million yen ($50,000) fine levied at Urawa Reds after their supporters hurled racial abuse at an away player.

"We will take into full account the changes in society since then and how clubs deal with these issues. We have made great efforts to get rid of discrimination. This is a real disappointment."

Yokohama could be ordered to play behind closed doors based on the results of a J-League tribunal, despite having identified the banana-wielding fan and banned him for life.

Urawa, Japan's best-supported club, had to play a match in an empty stadium as punishment after fans unfurled a "Japanese Only" banner earlier this year.

Yokohama president Akira Kaetsu said: "It's unforgivable. We do not tolerate any sort of discrimination."

Renato himself called the incident "regrettable", while Kawasaki's Japan striker Yoshito Okubo called for even harsher measures to be dished out to Yokohama.

"It should be a heavy punishment -- heavier even than for Urawa," he told the Nikkan Sports daily. "That punishment should not just be the supporter. The club has a responsibility. If they don't act, it's all over for the J-League. People need to be educated."

Yokohama defender Yuji Nakazawa blasted the F-Marinos fans.

"(Racism) has become a worldwide problem but everyone is supposed to know that it's not all right to have this sort of behaviour here too," said the former Japan centre-back.

"It's a shame, it's pathetic."

Yokohama and Kawasaki have a history of bad blood, with their fans clashing earlier this year. Incidents of racial taunts directed at opposition players have crept into the rivalry between the regional neighbours.