US officials say US national security would be “seriously harmed” if the letters were made public.

The New York Times quoted the US State Department's statement yesterday saying that the country's authorities will not release 22 emails from former Secretary of State Hillary Clinton because these letters contain "top secret" information, classified at the highest level of security of the US Government.

Former US Secretary of State Hillary Clinton. (Photo: New York Times)

US State Department spokesman John Kirby said the 37 pages of documents in Mrs. Clinton's personal letters were not classified at the time they were sent, but have now been upgraded to "top secret" because they include a lot of sensitive information.

Meanwhile, a senior US government official said that US intelligence agencies concluded that US national security would be "seriously compromised" if the above letters were published under any circumstances.

According to AP, 37 pages of documents in Mrs. Hillary's personal letters are considered top secret because they are related to "special access programs", including plans to deploy attacks using drones, or eavesdropping programs.

The US State Department's statement came three days before the first primary election of the 2016 presidential election campaign takes place in the state of Iowa.

The issue of Hillary Clinton's use of a personal email account while serving as US Secretary of State has caused the leading Democratic candidate to face many problems and criticisms, especially from Republican opponents.

The US government is expected to release some of Hillary’s 7,000 pages of emails. However, the 37 pages of “top secret” emails will definitely not be among them./.

According to VOV