Kenjiro Sano, who unveiled his logo design for the Tokyo 2020 Olympics last month, has denied allegations that he copied the design from an emblem for a Belgian theatre.

The Japanese designer told journalists there is "absolutely no truth" in claims that he plagiarised the logo while speaking at a press conference in Tokyo yesterday.

"I take a lot of time with every design, nurturing them like children," claimed Sano. "So for this kind of talk to emerge is really unfortunate and kind of sad."

Belgian designer Olivier Debie, who created the logo for the Théâtre de Liège in 2013, accused Sano of copying his symbol after the Olympics design was revealed in July 2015.

"I am extremely surprised to hear the remarks of the Belgian designer," said Sano. "I would like to take this opportunity to state that his claims are completely groundless."

"I was shocked and found it hard to accept, to be honest," he added. "But I've never been to Belgium, nor seen the logo even once."

Debie posted an image on his Facebook page presenting the logos side by side and tweeted an animation he created to show the similarities between the two designs.

Both logos feature a bold T shape, circles and graphic serifs. According to the games' organisers, Sano's design is based on the T in Tokyo, tomorrow and team, while Debie's combines the letters T and L that stand for Théâtre and Liège.

Even though his logo is not a registered trademark, Debie has reportedly asked the International Olympic Committee and Tokyo games organisers to change the logo, and threatened legal action if it is not withdrawn.

"Their logo was not a registered trademark, so there is absolutely no problem," said Tokyo 2020 marketing director Hidetoshi Maki.

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"In developing the emblems, Tokyo 2020 went through a regular verification procedure and chose the logo after a long, comprehensive and transparent process," added a statement from the games organisers.

"Prior to the announcement of the emblem, the IOC and Tokyo 2020 conducted extensive research on trademark protections internationally. We did not identify any particular issues through the thorough process and then became confident about releasing the emblem."

This isn't the first controversy to hit the Tokyo 2020 Olympics – last month Zaha Hadid's design for the stadium set to host many of its events was scrapped by the Japanese prime minister.

Copying claims also hit the last Olympic Games in London, when Thomas Heatherwick was accused of using Atopia's design for his petal-like cauldron.