A man shouted “die” as he doused an animation studio with fuel and set it ablaze in Japan today, public broadcaster NHK said, killing at least 33 people in the nation’s worst mass murder in nearly two decades. 

Prime Minister Shinzo Abe called the attack in the city of Kyoto - the latest grisly killing in a nation widely known for its low crime rates - “too appalling for words” and offered condolences. 

Police detained a 41-year-old man who shouted “die” as he poured what appeared to be petrol around the three-storey Kyoto Animation building shortly after 10am local time, public broadcaster NHK reported.

Fire engulfed the building and white and black smoke billowed from its charred windows. It was Japan’s worst mass killing since a suspected arson attack in Tokyo in 2001. 

Shiro Misaki, a 47-year old owner of a neighbourhood bar five minutes from the studio, said he was driving nearby when he saw the thick smoke.

“Policemen were stopping traffic and it was really hazy with smoke,” he said. “Even after I got back to my restaurant I could smell the smoke.”

The prime minister said the cause was arson.

“Today, many people were killed and wounded in an arson murder case in Kyoto,” Abe said in a post on Twitter. “It is too appalling for words.”

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

Kyoto police declined to comment. 

Kyoto, some 450km west of Tokyo, is the ancient capital of Japan and a major tourist draw for its ancient temples and cultural sites. 

The dead were found on all three floors of the building, including in the studio, and on a staircase leading up to the roof, the fire department said.

It was not clear if the roughly 10 people found dead on the staircase had been trying to escape. 

Thirty-six people had been taken to hospital by midday, the fire department said earlier, with 10 of them seriously injured. 

The fire department said it had completed its search of the building. 

Japanese animation, known as “anime”, includes television series and movies. A pillar of Japanese popular culture, it has become a major cultural export, winning fans around the world. 

Kyoto Animation produces popular series such as the 'Sound! Euphonium'. Its  'Free! Road to the World - The Dream' movie is due for release this month.

- Reuters