U.S. Marine Staff Sgt. Tyrone Luther Hadnott, 38, has denied raping the junior high school student, telling authorities he kissed her only, CNN reported. Authorities haven't charged Hadnott with the crime; under Japanese law, a person can be detained up to 10 days without being charged.

The U.S. Marine Corps in a statement acknowledged the detention but didn't mention Hadnott. The statement said the corps was investigating the incident.

The Japanese Foreign Ministry said it lodged an official protest with the United States.

The incident was reported Sunday in the Chanton entertainment district on Okinawa, CNN said.

"This type of crime violates the human rights of women. And taking the fact that the victim was a junior high school student, this kind of crime cannot be tolerated," Okinawa Gov. Hirokazu Nakaima said in a statement.

The matter sparked a protest Monday by a small group outside of the building where Hadnott was being held.