A box of dried feces was left in front of the Korean Consulate in the Japanese city of Yokohama on Saturday.

The flat 35-cm box was discovered by a consulate staffer in the parking lot.

A police bomb squad rushed to the scene but found only the excrement. Whether it was human or animal is unclear.

But a handwritten note identified it as "revenge" for a recent explosion at the Yasukuni Shrine in which a Korean is the prime suspect. The note also mentioned a rightwing Japanese organization that has led anti-Korean protests.

Meanwhile, a substance carried by the Korean suspect has been identified as potassium nitrate, an ingredient in gunpowder.

Japanese media earlier reported that Chon Chang-han (27) carried in his luggage a digital timer, batteries and a powdered substance.

Chon, who has voluntarily returned to Japan, is under arrest.

Responding to criticism that the suspect's personal information has been splashed all over the media, Japanese Chief Cabinet Secretary Yoshihide Suga said it was the press, not police, who revealed his name. "The Japanese government does not involve itself in media affairs," Suga said.