Fairfax has sacked Sydney Morning Herald contributor Mike Carlton after he refused to write his weekly column during a staff strike.

Fairfax announced on Tuesday it would cut five per cent of its full-time workers - 550 staff - across Australia and New Zealand, prompting a mass walkout at its offices including in Melbourne and Sydney.

Almost one third of the positions to go are journalists.

Carlton, a prominent media identity, was fired after refusing to cross the picket line to write his weekly column for the Herald's Saturday edition.

"I can confirm that Mike Carlton's agreement as a contributor to Saturday's Sydney Morning Herald has been terminated after he refused to file as normal his column for Saturday's morning paper," a Fairfax spokeswoman said on Friday.

The radio broadcaster's hosting job on the breakfast show on 2UE, also owned by Fairfax, has not been affected, management said.

"It's my understanding that Mike was unprepared to write during the strike," 2UE's general manager Simon Rufus told AAP.

"It's got (nothing) to do with the radio station. He'll be back on Monday."

The journalists' union said the sacking was a demonstration of what was wrong with Fairfax management.

"This is an indication again that the new regime at Fairfax Media is embarking on a low quality approach to journalism," a spokesman for the Media Entertainment and Arts Alliance said.

"The management prepared to trample on anyone who gets in their way and the people who will lose out in this case are the Sydney Morning Herald readers."

Printers at Fairfax Media, where journalists have gone on strike until Monday, are remaining at work, a union official has said.

Australian Manufacturers and Workers Union national print secretary Steve Walsh said the union was monitoring the situation but his members would keep working.

Journalists at Fairfax newspapers, including The Sydney Morning Herald and Melbourne's The Age, on Thursday voted to stay out until Monday over job cuts and pay negotiations.

The walkout comes just days after Fairfax Media announced it would cut 550 jobs under a business improvement program and Wednesday's sacking of The Age editor-in-chief, Andrew Jaspan.

"At this stage we are continuing to monitor the situation and maintaining a watching vigil," Mr Walsh told AAP.

He said he would be having discussions later Friday with the journalists' union - the Media, Entertainment and Arts Alliance.

"I will be in touch with the MEAA today to see what the latest (development) is."

The company's chief executive David Kirk says

Fairfax Media newspapers including The Age and The Sydney Morning Herald will be published as normal this weekend.

Mr Kirk said staff were striking illegally but declined to say if the company would take any action.

He said senior editorial staff and employees exempt from industrial action produced Friday's paper after Thursday's strike.

"We have a number of staff who are contractually exempt from industrial action," Mr Kirk told AAP.

"The plan is to continue to put out the newspapers absolutely as normal, and we are well advanced in doing that.

"We see no concern in getting the papers out tonight, Saturday and Sunday, and Monday, and beyond, if necessary."

Meanwhile, a senior Fairfax journalist has hit out at the company's "brutal" staff redundancy plans, saying further bureau mergers and cuts were being considered.

Sydney Morning Herald (SMH) senior writer Gerard Noonan said it was the wrong move by management when newspapers needed to refocus on quality, to combat the internet-sourced media.

"We have got a problem now with the company. It is being run by people who don't have ink in their veins," Mr Noonan told ABC Radio on Friday.

"And this latest act is basically bowing to the market, and saying we've got a market downturn here and what do we do, we reach for the knife.

"This is really a pretty brutal way of doing it."

Mr Noonan said Fairfax's Canberra-based reporters had successfully argued for more than 10 years for the retention of individual SMH and The Age political bureaus.

"In discussion that we've had in the last couple of days they've said not only the Canberra bureaus of the two great newspapers ... are on the table, but also so too are foreign bureaus (at risk of closure)," he said.

"You can slim it down to one bureau in Canberra covering everything, but you end up diminishing the analysis of the democratic process, and very seriously so."