KYOTO (REUTERS) - Many victims of an arson attack on an animation studio in the western Japanese city of Kyoto were young with bright futures, some joining only in April, the company president said on Saturday (July 20), as the death toll climbed to 34.

Thursday's attack on Kyoto Animation, well known in Japan and overseas for its series and movies, was the worst mass killing in two decades in a country with some of the world's lowest crime rates.

Company president Hideaki Hatta said many of the victims were young women.

"Some of them joined us just in April. And on the eighth of July, I gave them a small, but their first, bonus," he said.

"People who had a promising future lost their lives. I don't know what to say. Rather than feeling anger, I just don't have words," Mr Hatta said.

Fifteen of the victims were in their 20s and 11 were in their 30s, NHK said. Six were in their 40s and one was at least 60. The age of the latest victim, a man who died in hospital, was not known. The names of the victims have not been disclosed.

The studio had about 160 employees with an average age of 33, according to its website.

Police have confirmed the identity of the suspect as Shinji Aoba, but have declined to comment further.

Aoba had been convicted of robbery and carried out the attack because he believed his novel had been plagiarised, NHK and other media have said.

But Mr Hatta said he had no idea about any plagiarism claim, adding he had not seen any correspondence from the suspect.

Police have not arrested him, as he is being treated for heavy burns, NHK said, although police have taken the unusual step of releasing his name.

People living near the studio said they saw a man fitting Aoba's description in a nearby park the day before the attack.

Police suspect he may have spent a day or more in the area to prepare.

Resident Rie Bannai said her nephew saw the man sleeping on a bench in the park.

At the charred studio site, there was a growing mound of flowers brought by people who have come to pay their respects and pray.

Ms Bing Xie, 25, a Chinese student at Kyoto University, said she could not forgive the arsonist.

"The criminal who does this seems to have been mentally disturbed, but I can't forgive him. The young people at Kyoto Animation were beautiful and warm and it is hard to accept they are gone."

Police guarded the site as investigators, some on the roof near where many died in a connecting stairwell, examined the blackened building. The smell of burning lingered over the quiet suburban neighbourhood.

Mr Hatta said the building needed to be torn down because it was so badly damaged.

Tributes to the victims lit up social media, with world leaders and Apple Inc's chief executive offering condolences. The hashtag #PrayforKyoAni - the studio is known as Kyo Ani among fans - has become popular.

Kyoto Animation, in a quiet suburb about 20 minutes by train from the centre of Kyoto, produces popular "anime" series such as Sound! Euphonium. It is also known for Violet Evergarden, which has been shown on Netflix.