TOKYO

A blast has shaken a famous Japanese religious shrine at the heart of frictions with the Asian country's neighbors.

A Shinto festival was being held at Yasukuni Shrine at the time, but no injuries were reported.

State news agency Kyodo reported that police sent a bomb unit to the Tokyo shrine early Monday after an incendiary device is reported to have exploded in a public bathroom.

Public broadcaster NHK reported that a hole in the ceiling of the bathroom was discovered, as well as a battery and a lead wire.

Police have said they suspect a political motive in what is being seen as an attack.

The shrine has been a source of fierce tensions between Japan and its neighbors, especially China and South Korea, as it honors 14 war criminals convicted by the Allies in trials that followed World War II. 

The war continues to divide the three countries, with Chinese and Korean "comfort women" -- used by Japanese soldiers as sex slaves -- and differing perspectives in school history textbooks among the most recent issues to have provoked disagreement.

In Dec. 2013, a visit to the shrine by Japanese Prime Minister Shinzo Abe drew criticism, while conservative politicians in the country have been accused of repeatedly downgrading previous statements of apology for Japan's war past.

Abe himself has previously defended visiting sites like Yasukuni as a way of promoting peace by ensuring the past is not forgotten.