TOKYO: A suspected arson attack on an animation production company in Japan killed 24 people and injured dozens more on Thursday, with flames gutting the building in the city of Kyoto.

Police said the fierce blaze appeared to have been started deliberately, but there was no immediate information on a possible motive.

If arson is confirmed, the attack will be among the deadliest criminal acts in decades in Japan, where violent crime is very rare.

Hours after the blaze was brought under control, officials said at least 24 people were dead.

Among them were 14 people whose deaths were confirmed and another 10 who were in a state of "cardio-respiratory arrest", a term used in Japan to signify a victim's death before it is officially certified.

Emergency workers retrieved bodies from the ground, first and second floor of the building housing Kyoto Animation. Several were also found on a stairwell leading to the roof.

Officials said 36 people had been injured in the fire, 10 of whom were in serious condition.

"I saw people who were totally black or covered in blood, or who had suffered burns all over their body," a 53-year-old woman told the Kyodo news agency.

Around 70 people were believed to have been in the building when the blaze began, fire department officials said.

The fire sent thick white smoke pouring from the building's windows and left black charring on its facade.

- 'Lost for words' -

Japan's Prime Minister Shinzo Abe took to Twitter to express his horror.

"It's so dreadful that I'm lost for words," he wrote.

"I pray for those who passed away."

The fire department said it began receiving calls about the fire around 10:35 am (0135 GMT).

The blaze raged for more than three hours before being brought under control.

Police said they were still investigating the cause of the fire but it was a suspected arson attack.

"A man threw a liquid and set fire to it," a Kyoto prefectural police spokesman told AFP.

Public broadcaster NHK reported that a man had been detained in connection with the blaze and was later taken to hospital for treatment.

It reported that the suspect had poured a gasoline-like substance around the building and said "drop dead" as he set fire to it.

The eyewitness who spoke to Kyodo said one of the injured "claimed to have been splashed with kerosene or something like it".

Local media reported that the suspected attacker appeared to also have been armed with knives.

- 'Why, why, why?' -

Kyoto Animation's president Hideaki Hatta told reporters "there have been emails with death threats". without giving further details.

He said the building gutted by the blaze was "the core of the company", which has produced several well-known television anime series including "The Melancholy of Haruhi Suzumiya" and "K-ON!"

"It's unbearable that those who have led Japan's animation industry were hurt and lost their lives."

The blaze prompted an outpouring of support from those in Japan's anime industry, one of the country's best known cultural exports.

"No, I don't know what I should be thinking now," tweeted Yutaka Yamamoto, an animation director who once worked at Kyoto Animation.

"Why, why, why?"

An online fundraiser organised by an American anime licencing firm had raised over $220,000 by Thursday night.

Japan has a famously low crime rate. Arson is considered a serious crime and people convicted of deliberately setting fires in a country where many people still live in wooden houses can face the death penalty.

A man convicted of setting a fire that killed 16 people in Osaka in 2008 is currently on death row.

In 2016, a knife-wielding man went on the rampage at a care home for the mentally disabled, killing 19 in the country's worst mass killing in decades. —AFP