A man arrested after 19 people were killed in a knife attack at a centre for disabled people in Japan had reportedly written to parliament, asking for permission to kill.

Satoshi Uematsu had been involuntarily committed to hospital for two weeks earlier this year after he tried to present the letter to the speaker of the lower house of Japan's parliament, in which he expressed a willingness to kill disabled people if the government approved.

He was apparently released from hospital in early March.

Police arrested 26-year-old Uematsu, who was a former employee at the facility, after he handed himself in.

At least 25 other residents of the centre in Sagamihara - about 20 miles southwest of Tokyo - were wounded during the attack, 20 of them seriously.

Authorities confirmed the victims were 10 women and nine men aged between 19 and 70.

Staff at the Tsukui Yamayuri facility called police at around 2.30am on Tuesday after spotting a man armed with a knife in the grounds.

Officials said the attacker was held two hours later on suspicion of attempted murder and trespassing.

Police recovered a bag containing several knives, at least one stained with blood, according to an official.

The Asahi Shimbun newspaper reported the suspect told police: "I want to get rid of the disabled from this world."

NTV reported that the letter Uematsu allegedly wrote calling for euthanasia for disabled people said: "My goal is a world in which, in cases where it is difficult for the severely disabled to live at home and be socially active, they can be euthanised with the consent of their guardians."

Yoshihide Suga, chief cabinet secretary, told a news conference: "This is a very heart-wrenching and shocking incident in which many innocent people became victims."

The Japan Times reported that some residents and staff may have been tied up during the attack. The newspaper said that hospitals reported many of the injured had wounds to their necks.

Japanese radio station NHK said the suspect broke into the building by smashing a window.

Officials said Uematsu worked at the centre between December 2012 and February this year and left for "personal reasons".

According to the centre's website, it holds a maximum of 160 people including staff.

David McNeill is the Irish Times correspondent in Tokyo, and he gave more details to Newstalk Breakfast.