Liao Lyuyou, a Chinese citizen, was arrested for infiltrating and photographing a restricted area at Key West Naval Base, Florida on December 26.

According to the indictment filed in a federal court in Florida, southeastern America, Liao faced charges of breaking into military zones for the purpose of photographing defense equipment and state-level infringement.

Liao was indicted after infiltrating and photographing the U.S. Navy's air base in Key West, the site of the South American Interdisciplinary Forces, which oversees smuggling in the air and at sea.

Witnesses saw Liao walking along the security fence at Key West base in the early morning of December 26, then crossing a rocky beach close to the edge of the sea to cross the fence, even though there were many warning signs in the area. . Witnesses said they also warned Liao not to enter the base, but eventually they "still saw him entering the area and taking pictures".

A few minutes later, the military police came and interrogated Liao. He replied that he was only "photographing the sunrise". Liao was detained and later arrested by the Navy Crime Investigation Agency.

Noel Clay, a State Department spokesman, declined to comment. The US Navy did not comment.

Washington is concerned Beijing has stepped up espionage in the United States in recent years. US officials say China is its biggest intelligence threat.

Earlier, two Chinese diplomats were expelled by the United States after infiltrating a sensitive military base in the city of Norfolk, Virginia, where many secret US special forces units were stationed, in late September.

In September, US officials indicted a Chinese-American citizen suspected of being a Chinese government agent, accused of passing US secrets to China. Last December, a Chinese student was also charged with taking pictures of the Key West base.