Australia’s biggest newspaper rivals have made a rare showing of unity by publishing redacted front pages in a protest against press restrictions.

The News Corp Australia and Nine mastheads on Monday showed blacked-out text beside red stamps marked “secret”.

The protest is aimed at national security laws which journalists say have stifled reporting and created a “culture of secrecy” in Australia.

The government said it backed press freedom but “no one was above the law”.

In June, police raids on the Australian Broadcasting Corporation (ABC) and the home of a News Corp Australia journalist generated a huge backlash.

The media organisations said the raids had been conducted over articles which had relied on leaks from whistleblowers. One detailed allegations of war crimes, while the other reported an alleged attempt by a government agency to spy on Australian citizens.

The campaign on Monday, by the Right to Know Coalition, was also supported by several TV, radio and online outlets.

Michael Miller, executive chairman of News Corp Australia, tweeted an image of his blacked-out mastheads which include The Australian and The Daily Telegraph. He urged the public to ask of the government: “What are they trying to hide from me?”

The company’s chief rival, Nine – publisher of the Sydney Morning Herald and The Age – ran similar front pages.

ABC managing director David Anderson said: “Australia is at risk of becoming the world’s most secretive democracy.”

On Sunday, the Australian government reiterated it was possible that three journalists may face prosecution in the wake of the raids.

Prime Minister Scott Morrison said press freedom was important to Australia’s democracy, but added the “rule of law” needed to be upheld.

“That includes me, or any journalist, or anyone else,” he said on Sunday.

The findings of a press freedom inquiry will be tabled in parliament next year.

What are the demands of Press Organizations?

The campaign argues that tougher security laws enacted over the past two decades have threatened investigative journalism, eroding the public’s “right to know”.

Since new counter-espionage legislation was introduced last year, media outlets have lobbied for journalists and whistleblowers to be given exemptions to report sensitive information.

The organisations have also called for greater freedoms in other areas, such as reforms to freedom of information and defamation laws.