Zhao Qianli, 20, was sentenced to one year in prison and one year of supervised release

A 20-year-old Chinese student has been sentenced to a year in federal prison for illegally taking photos of a restricted naval base in Florida.

A federal judge in Key West imposed the sentence on Zhao Qianli after he pleaded guilty of one count of photographing defense installations on Tuesday.

Zhao's attorney insisted he was merely a tourist who got lost and wandered onto the base.

But investigators say he had only base photos on his cellphone and camera, and none of familiar tourist locations in Key West.

In addition to his prison sentence, Zhao must complete a year of supervised release.

Authorities say he took photos in September of sensitive areas of the Key West Naval Air Station after walking around a fence into a well-marked restricted zone.

According to court documents cited by CNN, Zhao entered the Joint Interagency Task Force South military property, located on Naval Air Station Key West, on September 26 without permission 'by circumnavigating the installation's primary fence line, and entering the military property from the beach.'

Zhao then went directly to an area that contains a range of satellite dishes and antennas called 'the Farm', and took videos and photos of the equipment in the area, court documents say.

The Joint Interagency Task Force South is located at Naval Air Station Key West, Florida

The court documents give no specific indication whether Zhao was attempting to commit espionage, CNN reported.

The Key West facility was referred to as 'one of the leading intelligence fusion centers in the world.'

It tracks more than 1,000 suspect targets a day, the US Navy says, turning intelligence images into virtual reality programmes.

Zhao was in the US to study musicology as part of a summer exchange program from North University of China.

The FBI said he was in the country legally, but his visa ran out a week before his arrest.