A man suspected of torching an animation studio in Japan shouted that he had been plagiarised and appeared to have planned the attack after a blaze killed 33 people.

In what is Japan’s worst mass killing in 18 year, media outlets reported the man, 41, “seemed to be discontented, he seemed to get angry, shouting something about how he had been plagiarised”, a woman told reporters.

Two cans, a rucksack and a trolley were found near the site, and television footage showed what appeared to be five long knives laid out by police as possible evidence on the ground outside the three-storey building.

Public broadcaster NHK said the man shouted “die” as he doused the three-storey Kyoto Animation building with fuel shortly after 10.30am on Thursday and set it ablaze.

Little is known about the man, who had no connection to the studio. He suffered burns to his legs and face and was under police guard in hospital.

Some of the victims were found in the studio, some on the third floor and others in a staircase leading up to the roof.

Late on Thursday night, authorities said another 10 people remained in a critical condition.

“I imagine many of the people who died were in their twenties,” said 71-year-old Kozo Tsujii, fighting back tears after laying flowers near the studio in the rain on Friday morning.

He said he drove by the studio on his daily commute: 
”I’m just very, very sad that these people who are so much younger than me passed away so prematurely,” he said.

A Kyoto City Fire Department official said fire engulfed the building as white and black smoke billowed from its charred windows in what was the nation’s worst mass killing since a suspected arson attack on a Tokyo building in 2001.

Prime Minister Shinzo Abe called the attack in the western city “too appalling for words” on Twitter and offered condolences.

The suspected arsonist was injured and was being treated in hospital, so police could not question him, NHK said.

it's sad to hear that my favorite studio who make the best anime being burned down. From nichijou to koe no katachi…I really enjoyed it…from the happy moment to sad moment…kyoani done everything to everyone.including me..get well soon everyone#PrayForKyoani pic.twitter.com/uCTOPZdMts

— Sphinx__97 (@sphinx__4) July 18, 2019

https://twitter.com/mhd_yassin017/status/1151822097322110979

Kyoto Animation, better known as KyoAni, was founded in 1981.

Best known for series Sound! Euphonium and the upcoming film Free! Road to the World – The Dream, it has about 160 staff and offices in Tokyo and Kyoto.

About 70 staff were thought to be in the Kyoto building at the time of the fire.

“I am heartbroken,”the studio’s chief executive Hideaki Hatta said.

“It is unbearable that the people who helped carry Japan’s animation industry were hurt and lost their lives in this way,” he said.

Mourners leave flowers outside the building where 33 people died in a fire on Thursday. Photo: AFP/Getty

There was an outpouring of support for the studio on Japanese-language social media, with some users posting pictures of animation.

Many posted with the hashtag #PrayForKyoani – using an abbreviation for Kyoto Animation.

The studio has a major influence on Japan’s animation industry that outstrips the list of works it has produced, Tokyo-based film commentator Yuichi Maeda said.

“It has a huge presence in animation here. To have this many people die at once will be a huge blow to the Japanese animation industry,” he said.

-with AAP