The Yasukuni shrine, which honors 2.5 million Japanese war dead, including executed war criminals, has been the target of criticism from China and South Korea, which suffered from Japan's World War II atrocities and aggression.

Tokyo police said in a statement that they received a call about an explosion and smoke at Yasukuni. Firefighters were also called to the scene and found the ceiling and walls of the restroom had been damaged, said an official at the Tokyo Fire Department, who spoke on condition of anonymity. But the fire was out by the time they arrived.

It was unclear what caused the explosion. Police and fire department officials declined to elaborate. Media reports said batteries and wirings that may be part of an explosive device were found. Police will be reviewing footage on security cameras for clues on who might be behind the explosion.

The shrine is a focal point for lingering tensions with Japan's neighbors over the country's aggression before and during World War II.

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