TOKYO - JAPANESE police said they tracked down a 10-year-old girl who put a notice on an Internet message board warning that she was going to kill another girl.

Believed to be the youngest person accused in a spate of similar Internet threat cases in Japan, the girl posted a message last month saying: 'I'm going to kill an elementary school girl on February 29 at 1.00 pm' in the Tokyo suburb of Saitama, police said on Wednesday.

She was tracked down after someone spotted the message and contacted police. Because of her age she was referred to counselling and was not arrested.

The girl was web-savvy as she has been surfing the Internet at home for the past two years, Mr Sakuma said.

'I assume she came across sites that had similar notices as the one she put up,' he said.

'Her parents were completely baffled as they said their daughter was usually calm and not in the least a troublemaker. They were aware their daughter surfed the Internet and so explained to her not to do such things,' he said.

Last month, police arrested a 23-year-old man for a similar online threat to kill a young girl, which triggered a security alert in suburban Tokyo.

The Internet and mobile telephones are nearly ubiquitous in Japan, even for the young. A recent survey found that about 60 per cent of 14-year-old students carried cellphones, with half using them to send 20 or more e-mail a day.