Nineteen people were killed and dozens were wounded after an attack by a knife-wielding man at a facility for the disabled in central Japan early on Tuesday, media reported, in Japan's worst mass killing in decades.
Police in Sagamihara, Kanagawa Prefecture, about 25 miles (40 km) southwest of Tokyo, have arrested Satoshi Uematsu, a 26-year-old former employee at the facility, Japanese media reported.
They said staff called police at 2.30am local time (1730 GMT Monday) with reports of a man armed with a knife on the grounds of the Tsukui Yamayuri-En facility.
The 3-hectare (7.6 acre) facility, established by the local government and nestled on the wooded bank of the Sagami River, cares for people with a wide range of disabilities, NHK said, quoting an unidentified employee.
Police had recovered a bag with several knives, at least one stained with blood, NHK said. No details were provided about where the knives were found.
The man, wearing a black T-shirt, did not have a knife when he turned himself in at a nearby police station, other reports said. Police said they were still investigating possible motives.
Asahi Shimbun reported that the suspect was quoted by police as saying: "I want to get rid of the disabled from this world."
Fifteen people were initially confirmed dead, while four were said to be in cardiac arrest, media reports said. Kyodo later said the death toll stood at 19.
There was confusion about the number of wounded, with reports fluctuating between 20 and 45.
Twenty-nine emergency squads responded to the attack, Kyodo reported, with those wounded taken to at least six hospitals in the western Tokyo area.
A man identified as the father of a patient in the facility told NHK he learned about the attack on the radio and had received no information from the centre.
"I'm very worried but they won't let me in," he said, standing just outside a cordon of yellow crime-scene tape.
The man, who arrived at the scene around 5am (2000 GMT Monday), said he had never heard of trouble at the facility before.
NHK reported that the facility is usually locked at night but the man broke into the building by smashing a window.
The facility's website said the centre had a maximum capacity of 160 people, including staff.
Social media went into overdrive as news of the mass stabbing broke. "I can't stop shaking. What a terrible incident, it's just too much," one post on Twitter said.
Such mass killings are extremely rare in Japan and typically involve stabbings due to Japan's strict gun laws.
Eight children were stabbed to death at their school in Osaka by a former janitor in 2001. Seven people died in 2008 when a man drove a truck into a crowd and began stabbing people in Tokyo's popular electronics and "anime" district of Akihabara.
Members of a doomsday cult killed 12 and made thousands ill in 1995 in simultaneous attacks with sarin nerve gas on five Tokyo rush-hour subway trains.