TOKYO, JAPAN - Most school children in Japan have experienced bullying, both as the victim and the perpetrator, a government report indicated on Friday.

Some 86.9 percent of elementary school pupils questioned said they were bullied - including being shunned by friends, ignored or talked about behind their backs - at least once in the past three years, the report said.

And 80.3 percent of junior high school students said they were picked on at least once in the same period, it said.

On the other hand, 84.0 percent of elementary school pupils said they had bullied their schoolmates at least once. The proportion came to 81.3 percent among junior high school students, it said.

"Anyone could be involved in bullying, which means bullying can occur no matter what the family backgrounds or individual characteristics," the report said.

While no particular factors are proven to cause school bullying, stress may be behind the phenomenon, the report said.

The poll, covering some 4,800 elementary and junior high school pupils aged between 10 and 15 in the Tokyo region, was carried out by the National

Institute for Educational Policy Research for three years from 2004. Bullying has long been a major educational issue in Japan due to concerns over the high suicide rate among schoolchildren who are picked on.