Updated 9.50am

A suspected arson attack on an animation studio in Japan on Thursday left 24 people dead and dozens injured, several of them seriously, the emergency services said.

The blaze in the city of Kyoto appeared to have been started deliberately, police said, but there was no immediate information on a possible motive.

"At least one unidentified person was confirmed dead," a fire department spokesman told AFP, adding that 37 others were hurt including 10 in serious condition. The death toll was later raised to 24.

The fire department said it began receiving calls around 10:35 am (0135 GMT) about the fire at the studio belonging to Kyoto Animation. The blaze was still burning two hours later.

"Callers reported having heard a loud explosion from the first floor of Kyoto Animation and seeing smoke," a fire department spokesman said.

He said the fire department had dispatched 35 fire engines and other fire-fighting vehicles to the site.

Police said they were treating the fire as a suspected arson.

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

Local media said a man had been detained in connection with the blaze, but there were no immediate details on the suspect.

Public broadcaster NHK said the suspect had been taken to hospital after suffering injuries in the fire.

There was no immediate statement from the company, which produced several well-known television anime series, including "The Melancholy of Haruhi Suzumiya" and "K-ON!"

"We are in the process of learning what happened," said a woman who answered the phone at the firm's headquarters in Uji City in the Kyoto region. 

"We cannot tell you anything more," she added.