The message, posted on a website by someone using a cellphone on June 15, came a week after a man posted similar warnings before killing seven people in a downtown Tokyo knifing rampage.

Since the deadly stabbing attack early this month, police have arrested several people for allegedly using the Internet to make chillingly specific threats of violence.

'I will go to Disneyland to stab visitors to death,' the 19-year-old male wrote, according to a police official in Chiba, the suburban area where the amusement park is located.

The suspect's name was not released because he is below the age of 20 and considered a minor under Japanese law.

Investigators have found no evidence that he was preparing to carry out a real assault, the official said on condition of anonymity, citing department policy.

Yesterday's arrest coincided with a search for a woman suspected of stabbing three people in the arm at a crowded train station in the western city of Osaka.

On Sunday, police released security camera footage showing a middle-aged woman in a black dress making what news reports interpreted as stabbing motions with her left hand.

No knife was visible in the video, and a large sun hat obscured the woman's face.

She was suspected of sneaking up from behind three women and then stabbing them. The victims suffered light injuries, according to a police spokesman who requested anonymity.

Japan has been on alert for copycat crimes in the wake of the June 8 mass stabbing that killed seven people and wounded 10 others.

The suspect in that attack, 25-year-old factory worker Tomohiro Kato, had apparently posted hundreds of threatening messages on the Internet before the incident, with the last one sent just 20 minutes before he started his knifing rampage.

ASSOCIATED PRESS