Extremists behind explosion near US base in Japan
http://www.dailytimes.com.pk/default.asp?page=story_20-11-2002_pg4_9
Thank you for the link
The blast occurred shortly after 11:00 pm Monday (1400 GMT) at a public park 500 metres (yards) from the US army’s Camp Zama, in Kanagawa, 40 kilometres (25 miles) southwest of Tokyo, police said. No one was injured in the attack, a Zama police spokesman said.
Police found a projectile launcher, a metal pipe about 55 centimetres (22 inches) long and about 5.5 centimetres in diameter, at the park as well as scorch marks on the ground, he said.
“The metal launcher was aimed at the US base and we suspect it was a guerrilla attack,” the official said, referring to Japanese radicals. Police found a second launcher, identical in design to the first pipe, and batteries in a thicket outside the park. “We have yet to find any explosives and I cannot confirm any projectiles actually entered the camp,” he said.
That's a report from 2002
Thank you for your link.