TOKYO - Japan's Meteorological Agency says a magnitude-6.8 earthquake has struck off the country's southern coast, and has issued a tsunami warning.

The agency said the quake hit Monday off the coast of Ishigaki island, near Japan's southern island of Okinawa, around 1,000 miles (1,600 kilometres) south of Tokyo. It struck at a depth of about six miles (10 kilometres).

There were no immediate reports of damage or casualties.