The victims were aged between 19 and 70, the Kyodo news agency, said citing the Sagamihara City Fire Department. Another 25 people were injured, 20 seriously. Both men and women were reported to be among the dead.
One doctor told NHK: "The patients are very shocked mentally, and they cannot speak now."
It appears that the attacker then left the facility himself, and drove to the Tsukui police station where he turned himself in.
Pictures have emerged of what is reported to be the steering wheel of his car, stained with blood.
"When Uematsu turned himself in, he was found carrying kitchen knives and other types of knives stained with blood," a Kanagawa official told reporters.