At least 19 people were killed and about 20 wounded in a knife attack at a centre for disabled people near Tokyo last night - Japan's worst mass killing in generations.
Police said they responded to a call at about 2.30am local time on Tuesday from an employee saying something horrible was happening at the Tsukui Yamayuri-en (Tsukui Lily Garden) centre in the city of Sagamihara, just west of the capital.
A man turned himself in at a police station in Sagamihara about two hours later.
Police said he left the knife in his car when he entered the station.
He has been arrested on suspicion of attempted murder and trespassing.
Local government officials identified the suspect as Satoshi Uematsu. Japan's national broadcaster NHK said he was 26 and another broadcaster, NTV, said he was upset because he had been sacked.
A Kanagawa district official told a news conference that Uematsu entered the building at about 2.10am by breaking a window on the first floor of a residential building at the centre.
Shinya Sakuma, head of the local authority's health and welfare division, said Uematsu had worked at the centre until February.
Police said there were several casualties but did not provide any numbers but the Sagamihara City fire brigade said 19 people died in the attack and that figure was confirmed by doctors at the scene.
A woman who lives opposite the centre told NHK: "I was told by a policeman to stay inside my house, as it could be dangerous. Then ambulances began arriving and blood-covered people were taken away."
Television footage showed a number of ambulances parked outside the centre, with medical and other rescue workers running in and out.
A White House statement expressed shock at the "heinous attack" and offered condolences to the families of those killed.
US National Security Council spokesman Ned Price said "there is never any excuse for such violence, but the fact that this attack occurred at a facility for persons with disabilities makes it all the more repugnant and senseless".
Mass killings are relatively rare in Japan, which has extremely strict gun control laws. In 2008, seven people were killed by a man who drove a lorry into a crowd of people in central Tokyo's Akihabara electronics district, then stabbed passers-by.
Fourteen were injured in 2010 by an unemployed man who stabbed and beat up passengers on two public buses outside a railway station in Ibaraki district, about 25 miles north east of Tokyo.
Chikara Inabayashi, who lives near the site of Tuesday's attack, said he was shocked such an outrage had happened in the quiet, semi-rural area near Mount Takao, a mountain popular with hikers.
"I never imagined such a horrible thing happening," he said. "I was astonished, that's the only thing I can say."
People living nearby described the centre as a friendly place whose staff and residents joined in community events.
Akie Inoue said her teenage daughter Honoka knew the suspect from events at the centre when she was at primary school.
"I was surprised to hear that the culprit was a person from this neighbourhood," she said.
"My daughter knew the culprit, I mean, they were acquainted. They would greet each other when they would meet and she tells me that he was a very kind person. We are all very shocked."
Honoka said: "He had a cheerful impression. He was the kind of person that would greet you first."
Japan's top government spokesman, chief cabinet secretary Yoshihide Suga, said: "This is a very tragic and shocking incident where many innocent people became victims.
"I sincerely pray for peace for the souls of those killed and extend condolences to the bereaved families as well as those wounded."
He said police and the government would work hard on the investigation "to grasp the whole picture".