An explosion has damaged the public toilets at Tokyo's controversial Yasukuni shrine, which honours Japanese war dead.

Yasukuni, which enshrines 2.5 million war dead, including executed war criminals, has been the target of criticism from China and South Korea, who suffered from Japan's Second World War atrocities and aggression.

Tokyo police said in 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 toilets had been damaged.

It was unclear what caused the explosion, in which no one was injured.

TBS TV news 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, TBS said.

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

Some Japanese politicians have insisted on making official visits in the name of patriotism, while others say such visits glorify Japan's historical mistakes.

Emperor Akihito has not visited Yasukuni and prime minister Shinzo Abe has also avoided making official visits over the last two years.

While views on the shrine have also divided the Japanese public, it holds emotional significance for many because during the war soldiers promised each other they would reunite at Yasukuni, if they died. Survivors and families say another monument elsewhere will not do because the soldiers' spirits go to Yasukuni.

Many families and tourists visit Yasukuni and today was a national holiday.

The shrine has a grandiose gate, giant cherry trees, flocks of pigeons and a museum that pays homage to those who died in Japan's wars, including kamikaze pilots.