Two older woman suffered minor injuries on the island, about 1,500 kilometers southwest of Tokyo, local officials said.
The agency said a tsunami wave up to 10 centimeters high washed over the coast after the 5:31 a.m. (2031 GMT Friday) quake.
It had issued a tsunami warning for coastal areas of Okinawa prefecture soon after the tremor and warned residents to move away from the coast, but the warning was downgraded to an advisory around one hour later and then withdrawn.
Police had received a report of ruptured water pipes in cities that included Naha, the capital of Okinawa, but no major damage.
The quake, the strongest to hit off Okinawa since 1909, was centered 10 kilometers underground in waters about 80 kilometers southeast of Naha.
The US Geological Survey measured the latest quake to hit earthquake-prone Japan at a magnitude of 7 and said aftershocks of magnitudes 5.1, 4.9 and 4.8 followed over the next nine hours.
After the initial quake, a 74-year-old woman in Naha was injured when she fell out of bed while a 66-year-old was also hurt when she fell in her house, local authorities said.
