The United States plans to announce espionage charges Monday against five Chinese individuals in the military who are believed to have spied on American companies and stolen trade secrets, a U.S. government official familiar with the matter said.

With the charges, the U.S. Justice Department would be publicly accusing China of cyber spying for the first time.

Attorney General Eric Holder and other U.S. officials will hold a news conference at 10:00 a.m. EDT (1400 GMT) "to announce a criminal indictment in a national security case."

The department has not named the Chinese individuals involved or the U.S. companies targeted. More details are expected in documents relating to the charges, which are expected to be made public later on Monday.

NBC News reported on Monday that the targeted American companies involve those in the energy and manufacturing sectors. A separate report by the Wall Street Journal Monday said the U.S. planned to charge five people allegedly linked with the People's Liberation Army.

American officials have long been concerned about hacking from abroad, especially China. Secret U.S. State Department cables obtained by WikiLeaks traced major systems breaches to China, Reuters reported in 2011. One 2009 cable pinpointed attacks to a specific unit of China's People's Liberation Army.

Such charges, however, are symbolic but the move would prevent the individuals indicted from traveling to the United States or other countries that have an extradition agreement with the United States.

Several cyber security experts said Monday's action showed the United States was serious about tackling the hacking concerns.

"It sends a strong message to the Chinese," a senior fellow at the Center for Strategic and International studies James Lewis told Reuters.

Others some remained skeptical the move would deter such online invasions.

"It won't slow China down," said Eric Johnson, an information technology expert at Vanderbilt University and dean of its School of Management.

An FBI official last week told Reuters to expect multiple cyber security-related cases, including indictments and arrests, in the coming weeks.

On Sunday, a top Chinese Internet official called for Beijing to tighten its own cyber security, citing "overseas hostile forces."