Journalists at Fairfax newspapers including The Sydney Morning Herald and Melbourne's The Age have voted to strike until Monday over job cuts and pay negotiations.
Today's walkout comes just days after Fairfax Media announced it would cut 550 jobs under a business improvement program.
The journalists say they are angry at a lack of consultation from management and will not be "treated like animals".
Journalists at Fairfax's Sunday publications, the Sun-Herald and Sunday Age, as well as NSW regional titles The Herald in Newcastle and the Illawarra Mercury, also have voted to strike until Monday.
Senior Age journalist Michael Bachelard said staff at the Melbourne broadsheet at Thursday's afternoon's stop work meeting were angry about the cuts and long-term delays in pay negotiations.
"Age staff are passionate about their masthead and their readers, and are disappointed that the managers of the company appear willing to sacrifice quality journalism for the sake of the bottom line," Mr Bachelard said.
"We'll make the same demands we have from the beginning - that the company negotiates with us on Enterprise Agreements and to have the guts to inform us properly about the cuts."
Victorian branch secretary of the Media Entertainment and Arts Alliance, Louise Connor, said staff were angry at a lack of consultation from management.
"We're not going to be treated like animals," Ms Connor said.
Crucial Fairfax printers in Sydney and Melbourne have remained at work, ensuring the papers will come out on Friday at least.
"The last I heard there was no stop work activity," Australian Manufacturers and Workers Union national print secretary Steve Walsh said.
"It is work as usual. Obviously we support the actions of the MEAA. We will continue to monitor the situation but at this stage things are proceeding normally."
Fairfax Media deputy chief executive officer Brian McCarthy said the industrial action by editorial staff "is disappointing".
"Publishing arrangements are in place and we anticipate all our newspapers will be published as normal over this period," he said in a short statement posted on the Sydney Morning Herald and The Age websites.
The job cuts, which affect five per cent of the Fairfax workforce in Australia and New Zealand, are being made under a new business improvement program to save $50 million a year, the company said on Tuesday.
The first high profile victim of the 550 job cuts came on Wednesday when Age editor Andrew Jaspan was sacked after four years at the helm.
The cuts will include 180 editorial jobs.
Fairfax, which merged with Rural Press in 2007, recorded a net profit of $386.9 million for 2007-08, up from $263.51 million the previous year.
MEAA spokesman Mike Dobbie said staff fear journalism standards will plummet under the new management.
"People are worried about their futures and if they are going to have a job in a few weeks time," Mr Dobbie said.
"They believe the new management team that has come in since the merger with Rural Press is all about low cost and low quality journalism."