TOKYO—An explosion that struck the controversial Yasukuni Shrine in Tokyo on Monday may have been a politically motivated attack, police said.
No one was injured in the blast, which hit at 10 a.m. local time ahead of a ceremony to celebrate the autumn harvest, on a national holiday in Japan.
At the time of the incident, about 20 Shinto priests and 100 worshipers were in the main building of the shrine to attend the celebration. The event continued as scheduled.
The explosion occurred in a public bathroom near the shrine’s southern gate, just outside the main building. No arrests have been made in connection with the blast, which charred the walls of the bathroom and left a small hole in the ceiling, according to local media, which reported that investigators found batteries and wire at the scene.
A popular sightseeing spot, a steady stream of visitors continued at the shrine after the blast, many of them unaware of the incident.
The shrine has been the target of political radicals in the past. On New Year’s Eve last year, a 25-year-old Japanese man was arrested after he set fire to one of the shrine structures. In 2013, a South Korean man was arrested for entering the compound with inflammable liquids.
Yasukuni is widely seen—including by some people in Japan—as a symbol of the country’s militarism before and during World War II. Among the 2.4 million war dead enshrined are 14 convicted class-A war criminals.
Visits to the shrine by Japanese prime ministers, including Shinzo Abe in December 2013, provoke outrage in China and South Korea, which were invaded by Japan.
Many Japanese on the political left warn about a return of that militarism, and there was widespread anger at the Abe government’s passage in September of legislation expanding the overseas role of the country’s military. The bills, which cast off restrictions that had been in place since the end of World War II, prompted months of street protests and even led to scuffles in parliament.
Opinion polls consistently showed that the bills were opposed by a slim majority of Japanese.
Visitors to the shrine on Monday expressed anger at the incident. Yoshitaka Uchiyama, a 75-year-old visitor to the shrine, said he was “very offended” by Monday’s act.
A group of retirees from Niigata Prefecture, which is about 200 miles north of Tokyo, were also at the shrine. “Very sad,” said one of the women, whose group decided to go ahead with the trip despite learning about the blast while on their way to the city.
Write to Mitsuru Obe at mitsuru.obe@wsj.com