Three 18-year-old boys are in custody for kicking to death a rabbit they stole from a Tokyo elementary school last year, police said Wednesday.

Police said the three teens, whose names are being withheld because they are minors, have confessed to the crime, which is a violation of the animal protection law.

"We kicked it like a soccer ball," police quoted one of the teens as saying.

One boy was arrested and fresh warrants were served on the other two, now being held for a motorcycle theft, for animal abuse. Their cases have been sent to prosecutors.

The trio broke into the school in Koto Ward on May 8, stole the rabbit kept there for the students, and took it to a park 1 km away where they killed it, police alleged. Two of the teens had attended the school.

"In the beginning, we were just having fun, but things got out of hand," one of the teens reportedly told police.

The rabbit's carcass was thrown into a river in a plastic bag weighted with rocks, police said.

The incident surfaced after the pair were collared in the motorcycle theft. The boys belong to a teen gang.