ASIO has entered the ABC's Melbourne headquarters to secure more classified cabinet files.

Members of the domestic spy agency entered the Southbank office about 5:00pm (AEDT).

The files were placed in a safe provided by the agency, which the ABC can access.

It follows early morning operations at the ABC's Parliament House bureau and its Brisbane offices to secure documents obtained as part of The Cabinet Files breach.

Officers entered both premises about 1:00am (AEDT) and ensured the documents were placed in the safes.

Two ASIO officers arrived at the Melbourne ABC offices about 5:00pm on Thursday. ( ABC News: Danielle Bonica )

The ABC obtained hundreds of classified documents, which were inside two locked, ex-government filing cabinets sold second-hand in Canberra.

Some of the files are marked "AUSTEO", which means they are to be seen by Australian eyes only. Some also relate to national security.

The ABC has published some of the documents obtained, but withheld many of the files for national security reasons and to protect the privacy of public servants.

ABC news director Gaven Morris has defended the decision to publish as clearly in the national interest and argued the ABC has been responsible and "as careful as we could possibly be".

"We haven't gone anywhere near stories or issues that may have a national security implication," he said.

He said once the story was published, the broadcaster had worked with the Government on the future of the documents.

"This was an agreed process with the Government, we wanted to ensure that as the national broadcaster we were doing all we could to work to ensure the documents were safe," Mr Morris said.

Talks are continuing between lawyers for the ABC and the Department of the Prime Minister and Cabinet.