The five-day event off the southern island of Jeju had initially included the Japanese navy, whose plan to fly the flag caused fury and a series of anti-Tokyo protests in its former colony.

The emblem has been an ensign for Japan's Maritime Self-Defence Forces since 1954, but is seen in much of east Asia as a symbol of its military aggression during the Second World War.

Koreans remain resentful of Japan's 1910-45 colonisation of the peninsula and the neighbours -- both of them US allies --- have often locked horns over issues of history and a territorial row over Seoul-controlled islets also claimed by Tokyo.

Tokyo last week withdrew from the review after Seoul's navy asked all participating countries to display only their national flag and the South's on their vessels.

Tokyo dismissed the request, arguing that it was mandatory to fly the "Rising Sun" flag under Japanese law.

"The event started this morning as scheduled," a spokesman for the South's navy told AFP.

A total of 13 countries including the South, the US, Russia and India are set to show off 41 warships -- including the USS Ronald Reagan aircraft carrier -- and more than 20 military planes at this year's event, with the main display on Thursday.

Russia and the US have sent the largest contingents, with three warships each, Moscow's including the Varyag missile cruiser. China has sent delegates but no vessel.