The U.S. military is banning and blocking employees from visiting The Intercept in an apparent effort to censor news reports that contain leaked government secrets.

According to multiple military sources, a notice has been circulated to units within the Army, Navy, Air Force, and Marine Corps warning staff that they are prohibited from reading stories published by The Intercept on the grounds that they may contain classified information. The ban appears to apply to all employees—including those with top-secret security clearance—and is aimed at preventing classified information from being viewed on unclassified computer networks, even if it is freely available on the internet. Similar military-wide bans have been directed against news outlets in the past after leaks of classified information.

A directive issued to military staff at one location last week, obtained by The Intercept, threatens that any employees caught viewing classified material in the public domain will face “long term security issues.” It suggests that the call to prohibit employees from viewing the website was made by senior officials over concerns about a “potential new leaker” of secret documents.

The directive states:

We have received information from our higher headquarters regarding a potential new leaker of classified information.  Although no formal validation has occurred, we thought it prudent to warn all employees and subordinate commands.  Please do not go to any website entitled “The Intercept” for it may very well contain classified material.

As a reminder to all personnel who have ever signed a non-disclosure agreement, we have an ongoing responsibility to protect classified material in all of its various forms.  Viewing potentially classified material (even material already wrongfully released in the public domain) from unclassified equipment will cause you long term security issues.  This is considered a security violation.

A military insider subject to the ban said that several employees expressed concerns after being told by commanders that it was “illegal and a violation of national security” to read publicly available news reports on The Intercept.

“Even though I have a top secret security clearance, I am still forbidden to read anything on the website,” said the source, who spoke on condition of anonymity due to the sensitivity of the subject.  “I find this very disturbing that they are threatening us and telling us what websites and news publishers we are allowed to read or not.”

(If you work for the military or the government and have received similar instructions, please let us know.)

On Monday, staff within the Navy, Army, and Marine Corps separately confirmed that they could not access The Intercept from work computers. Two Navy sources said that if they tried to view the site they were served with the insignia of the Strategic Command and a warning that they were “attempting to access a blocked website” that had been barred for “operational reasons” by a Department of Defense filtering system.

An Army spokesman had not responded to a request for comment at the time of this article’s publication. Marine Corps spokesman Capt. Eric Flanagan admitted that Marine Corps staff were notified “as a precautionary measure that may contain classified information.” The Navy and Air Force both referred requests for comment to the Department of Defense.

In an emailed statement, Defense Department spokeswoman Lt. Col. Valerie Henderson said that she had not been able to establish whether the DoD had been the source of “any guidance related to your website.” Henderson added, however, that “DoD personnel have an obligation to safeguard classified information. Classified information, whether made public by unauthorized disclosure, remains classified until declassified by an appropriate government authority. DoD is committed to preventing classified information from being introduced onto DoD’s unclassified networks.”

Earlier this month, after the publication of two Intercept stories revealing classified details about the vast scope of the government’s watchlisting program, Reuters reported that “intelligence officials were preparing a criminal referral” over the leaks.

The ban on The Intercept appears to have come in the aftermath of those stories, representing the latest in a string of U.S. military crackdowns on news websites that have published classified material. Last year, the Army admitted that it was blocking parts of The Guardian’s website after it published secret documents from former National Security Agency contractor Edward Snowden. In 2010, WikiLeaks and several major news organizations were subject to similar measures after the publication of leaked State Department diplomatic files.

Flanagan, the Marine Corps spokesman, told The Intercept that The Washington Post was also blocked by some military agencies last year after it published documents from Snowden revealing covert NSA surveillance operations.

“Just because classified information is published on a public website, that doesn’t mean military people with security clearance have the ability to download it,” Flanagan said.