A 12-year-old boy erroneously voted Saturday in the early in-person voting for Sunday's Lower House election, the election administration committee of Hakodate in Hokkaido said.

The boy cast the vote at an advance voting booth set up at a shopping center in the city, using a ballot belonging to his 50-year-old mother.

The committee acknowledged that the incident occurred due to insufficient checks as it was in a hurry to deal with an onslaught of people casting early ballots. The vote will be treated as valid because it cannot be distinguished from the rest.

According to the city's election administration committee, the boy visited the polling station with his father, 47, at around 5 p.m. Saturday and tried to vote on behalf of his mother, who was not feeling well, at his father’s request.

A total of three staff members in charge of accepting voters, checking the list of voters' names and issuing the ballot papers failed to notice any irregularities with him, and he cast a ballot for the single-member district.

Immediately afterwards, one of the staff members who had overlooked him earlier felt something was wrong and stopped him, preventing him from voting for the proportional representation and the national review of Supreme Court judges.