North Korea dispatched covert commando teams to the United States in the 1990s to attack nuclear power plants and major cities in a conflict, according to a declassified Defense Intelligence Agency report.

The DIA report, dated Sept. 13, 2004, reveals that five units of covert commandos were trained for the attacks inside the country.

According to the report, the "Reconnaissance Bureau, North Korea, had agents in place to attack American nuclear power plants."

The document states that the North Korean Ministry of People's Armed Forces, the ministry in charge of the military, "established five liaison offices in the early 1990s, to train and infiltrate operatives into the United States to attack nuclear power plants and major cities in case of hostilities."

"One of the driving forces behind the establishment of the units and infiltration of operatives was the slow progress in developing a multi-stage ballistic missile."

North Korea is known to have at least two long-range missiles capable of hitting the United States, the Taepodong-2 intercontinental ballistic missile, and the KN-08 road-mobile ICBM, which has not yet been flight tested.

The report indicates that power plants would be targeted for attack "in the event of hostilities between the United States and DPRK" – the acronym for the Democratic People’s Republic of North Korea.

The Reconnaissance Bureau is part of the Ministry of People’s Armed Forces and is in charge of the estimated 60,000 North Korean special operations commandos.

The heavily redacted report is what is known as a raw intelligence report, consisting of information possibly provided to the United States by a defector or agent, or possibly obtained from electronic surveillance.

Reconnaissance Bureau commandos have undertaken terrorist operations in the past in South Korea and other locations.

But the DIA report is the first intelligence document indicating North Korea had planned attacks inside the United States and dispatched agents for the operations.

Disclosure of the report, obtained under the Freedom of Information Act, comes amid threats by presumed North Korean agents to conduct September 11-style terrorist attacks against U.S. movie theaters.

The threats coincided with efforts by North Korea to prevent the showing Dec. 25 of the Sony Pictures film "The Interview," a comedy involving a fictional plot to assassinate North Korean leader Kim Jong Un.

The U.S. government determined that the massive hack targeting against Sony, which stole an estimated 100 terabytes of data including unreleased films, has been determined to be the work of North Korean hackers or those working for the regime of Kim Jong Un.

S.Y. Lee, a Department Homeland Security spokesman, declined to comment on the 2004 document.

A DHS official said the department is aware of the threat to attack movie theaters.

"We are still analyzing the credibility of these statements, but at this time there is no credible intelligence to indicate an active plot against movie theaters within the United States," the official said.

The official said DHS will adjust its security procedures to protect Americans.

"This includes continued, regular information sharing with our state, local, federal and international partners, builds on ongoing work, such as enhanced protection at federal facilities," the official said, adding that the public is encouraged to report suspicious activity to law enforcement agencies.

The FBI, in response to a Freedom of Information Act request, said it was unaware of the DIA intelligence report on North Korean commando teams. In a July 9, 2012 letter, the FBI stated that it was unable to find any file records on North Korea's Reconnaissance Bureau.

An FBI spokesman had no immediate comment. A DIA spokesman did not return emails seeking comment on the documents.

A second DIA document reveals that an American defector identified only as "Jackson" and as a former Air Force officer was working inside North Korea for the Reconnaissance Bureau.

The 1998 document stated that the officer had been "captured by North Korea" and was teaching North Koreans "U.S. Special Forces tactics, English [language], and interrogation techniques as chief of psychological operations studies at Madonghui Military College to North Korean seaborne snipers."

The American also "visited the 52nd Seaborne Sniper Battalion to teach U.S. Special Forces tactics, American English, and interrogation techniques since before 1983," the report said, noting that the training was carried out under the Reconnaissance Bureau.

The reference to "American English" is an indication the training may have been preparation for the future dispatch of North Korean snipers to the United States.

Mark Sauter, a security adviser to corporations and long-time North Korea watcher said the documents clearly raise alarms about whether North Korea could follow through on threats to conduct 9/11-style terrorist attacks.

"What they’ve done by the Sony hack is shown they’re certainly willing to attack a U.S. corporation," said Sauter, who obtained the documents. "Now they’re threating a physical attack along the lines of 9/11 and it is certainly possible they could have agents inside the United States capable of carrying out terrorist attacks."

"North Korean agents have committed terrorist attacks and kidnappings around the world," said Sauter, a former Special Forces and infantry officer. "Why wouldn’t they send agents to the homeland of their biggest enemy?"

Sauter noted that it took the U.S. government weeks to determine that North Korea was capable of hacking a major company. "It would be a mistake for the government now to assume North Korea is not capable of launching a terrorist attack in the U.S.," he said. "They may or may not have the desire to attack the U.S. homeland now or in the future, but there’s a good chance they have at least some capability."

Bill Cowan, a retired Marine officer, agreed and called the document an alarming disclosure.

"This demonstrates the North Koreans have capabilities most of us didn’t realize they had," Cowan said. "It talks about them being on U.S. soil to carry out attacks and that takes the threat to a whole new level. And they’re probably still here."

Past Reconnaissance Bureau operations included the bombing in Rangoon, Burma in 1983 in an attempt to kill then-South Korean President Chun Do-hwan. Three senior South Korean government ministers were killed in the attack.

Bureau commandos also carried out the attack on South Korea’s presidential Blue House in 1968 in an attempt to assassinate then-President Park Chung Hee, father of current South Korean President Park Geun-hye.

The Reconnaissance Bureau also is in charge of covert operations to infiltrate South Korea through tunnels and seaborne insertion of intelligence personnel.

North Korean intelligence activities in the United States have been limited.

In 2003, the FBI arrested Korean-American businessman John Joungwoong Yai, who was identified as a North Korean agent. He pleaded guilty to financial charges and served two years in prison.

Yai was paid for sending reports to North Korea through China based on publicly available sources. He had been tasked by North Korean officials to locate a North Korean agent who had defected.

Documents in the case revealed plans by North Korea to try and plant one of its agents inside the U.S. government.