Striking junior doctors took to the streets today to protect safer working hours for them in public hospitals.

About 3000 junior doctors began a two-day strike at 7am this morning in a battle with their district health board employers.

They're backed by nurses who are calling on DHBs to settle the row quickly.

Striking junior doctors were out picketing outside Auckland Hospital when the strike began.

Fresh in the minds of many was the last war between junior doctors and their employers two years ago over safer hours.

It ended in early 2017 with a deal under which the number of days doctors could work in a row was cut from 12 to 10.

Photo: RNZ / Brooke Jenner

But picketing North Shore doctor Alyssa Page says while that's good, many days are still very long.

"So within those 10 days we still have two 15-hour days and after 4pm, one doctor can be responsible for up to 200 patients and if two for those patients become very unwell to the point their lives are at risk it actually be quite unsafe."

Many doctors believe their employers intend to hold out against them and their union, the Resident Doctors Association (RDA) until late February when only one employment deal may be available to doctors - one the RDA doesn't support, she says.

"We feel the DHBs are holding out until it does expire so that they can implement the new ... MECA (Multi-Employer Collective Agreement) other doctors have."

Another doctor, Ivor Popovich, says long hours go with the work, but that's not all there is to it.

"We know we are going to work long hours but all we want in return is to maintain what we've fought to achieve for the last long while in our contract and not have that eroded or taken away," he said.

Photo: RNZ / Brooke Jenner

The organiser of the Auckland picket, emergency department doctor Christina Vanderboor, said they were fighting now to retain the improved hours they won in 2017 so they can address long days as well.

"You're trying to make decisions and you're trying to focus on reading an ECG or reading lab results and you really have to focus your brain. That's just to do the bare minimum of work and trying to see what's wrong with patients and trying to fix them."

DHBs have rejected the view they want to claw back or reduce the 2017 deal, saying they only want better flexibility at the local level.

But nurses are also on the doctors' side, with the Nurses Union's industrial advisor, Lesley Harry, today urging DHBs to settle the row.

"We don't support unsafe rostering practices. We're aware that junior doctors have over a long, very long period of time, worked excessive hours," she said.

DHBs contingency planner Anne Aitcheson said hospitals are fuller and busier than they'd planned to be during the strike, but they were managing well.

"It means that some of the people who are covering some of our rosters may have to work longer shifts today, but that's all part of the preparation that has been ongoing for the past couple of weeks."

She's urging anyone who is sick to go to hospital rather than staying away.

Junior doctors are on strike until 7am on Thursday.