Japan’s sumo wrestlers have been warned to keep their shoes on when they are not training – to avoid being bitten by venomous fire ants.

The warning comes after fire ants were spotted in Japan for the first time in May, believed to have been carried into the country on board a container from eastern China.

Since then, there have been a growing number of sightings of the South American insects across the country, including Tokyo, Osaka and Nagoya, as well as inland regions.

The continued sightings of fire ants prompted the Japan Sumo Association to issue an official fire ant warning to wrestlers competing this week in the Nagoya Grand Sumo Tournament.