Senator Kristina Keneally has demanded answers from the government as federal police raid the ABC offices in Sydney's Ultimo over a series of stories alleging war crimes in Afghanistan.

"Freedom of the press is an essential component of our democracy," Keneally said in a statement released shortly after the raids began on Wednesday.

"Media freedom is at the core of our democratic society.

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"Labor has requested a briefing through the Home Affairs Minister’s office to seek to understand why raids of such nature are warranted.

"Minister Dutton must explain what he knew about these two raids – one on a journalist’s home and one on the ABC."

The series at the centre of Wednesday's raid, titled The Afghan Files, was published in July 2017.

The ABC says the series, related to Australia's elite special forces in Afghanistan, revealed "hundreds of pages of secret Defence Force documents leaked to the ABC (which) give an unprecedented insight into the clandestine operations of Australia's elite special forces in Afghanistan including incidents of troops killing unarmed men and children".

The ABC reported at the time that some of the cases detailed in the documents were being investigated "as possible unlawful killings".

The ABC on Wednesday reported that warrants indicated AFP officers would be searching documents and computers linked to reporters Dan Oakes and Sam Clark as well as news director Gaven Morris.

Treasurer Josh Frydenberg has refused to answer questions or give his opinion about the raid.

"We respect the independence of the fourth estate but at the same time this is an ongoing investigation - it would be inappropriate to for me to comment," Frydenberg told a press conference.

Canberra raid

ABC executive editor John Lyons tweeted that ABC lawyers asked the AFP if there was any connection with a raid on News Corp Australia journalist Annika Smethurst on Tuesday and the police said "No".

The AFP raided Smethurst's Canberra home over a 2018 story detailing an alleged government proposal to spy on Australians.

It has since confirmed that the activity was not linked to the search warrant executed in Canberra on Tuesday.

Lyons on Wednesday tweeted that ABC lawyers had told the AFP officers: "We waive no rights, and reserve right to take injunction against the warrant."

The Australian Federal Police said the raid was "in relation to allegations of publishing classified material contrary to provisions of the Crimes Act".

"The search warrant relates to a referral received on July 11, 2017, from the chief of the Defence Force and the then-acting secretary for Defence," the AFP said in a statement.

The federal police says the warrant was duly authorised and no arrests were planned.