The court and police declined to confirm the reports.
A suspicious package that prompted the cancellation of a hearing for the man accused of murdering former Japanese prime minister Shinzo Abe contained only a petition, and no explosives, local media said Tuesday.
Tetsuya Yamagami had been due to make his first appearance before a court in western Japan's Nara on Monday, accused of shooting the former leader last July.
But the session was "cancelled as staff were evacuated from the building after a suspicious item was delivered to the court", a court spokesman told AFP.
Police were called after the object set off a metal detector, local police said.
It was then moved to an open area, where bomb specialists in protective gear investigated.
"But no explosives or hazardous substances were found," a police spokesman told AFP, without giving further details.
Public broadcaster NHK said the box contained a printout of a Change.org petition seeking a lenient sentence for Yamagami.
The petition has amassed 13,000 signatures since last year, and its organiser admitted to NHK that they had sent the document to the court.
"I sent the signatures in the hope that they would be seen by as many interested parties as possible," the broadcaster quoted the person as saying, without identifying them.
"As they were thick and it was raining, I put them in cardboard boxes... There was never any intention to obstruct justice."
The sender contacted the police themselves after learning that the box had triggered a security alert, the Kyodo news agency said.
The court and police declined to confirm the reports.
Yamagami, 42, faces charges of murder and violation of arms control laws, and could face the death penalty if convicted.
He reportedly targeted Abe -- Japan's best-known politician and longest-serving prime minister -- over his ties to the Unification Church, the global sect whose members are sometimes referred to as "Moonies".
The suspect is believed to have resented the church over large donations his mother made that bankrupted his family.
Details of his upbringing have stoked anger in Japan against the Unification Church and garnered Yamagami sympathy, with supporters sending him donations and signing the petition calling for leniency.
The Unification Church was founded in Korea in the 1950s by self-styled messiah Sun Myung Moon.
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