NHS bosses are aiming to keep nearly all services running as resident doctors begin a five-day walkout in England.

The strike – the 13th by British Medical Association members in the long-running pay dispute – began at 07:00 GMT and lasts until 07:00 Wednesday.

Resident doctors – the new name for junior doctors – will walk out of both emergency and non-urgent care.

Hospitals will come under the most strain, with resident doctors making up about half the medical workforce. But NHS England said patients should still attend appointments unless advised otherwise.

It said it wanted to keep 95% of non-urgent work, such as hip and knee operations, going.

The NHS aims to do this by re-deploying and offering overtime to consultants and and other senior doctors as well as relying on those not striking – around a third of resident doctors are not BMA members.

But this will come at significant cost with the NHS estimating the five-day walkout is costing £240m to cover.

Despite the attempt to keep services going, patients like Colette Houlihan, 68, have still had to face postponements.

She was due to have a pre-surgery appointment on Monday, but this has now been pushed back to late December.

Ms Houlihan, from Cambridgeshire, who is waiting for a benign tumour in her neck to be removed, said she had had to put up with two cancellations already, but could understand those as she was told patients who were higher priorities needed to be seen.

“They could have had cancer. I didn’t mind that, but this is different.

“I am furious. By striking they ignore the Hippocratic Oath – first and foremost do no harm.

“Striking causes harm by way of delaying procedures, taking senior doctors from their posts and causing chaos within the system,” she said.

NHS England medical director Prof Meghana Pandit said it was frustrating and disappointing that there was another round of industrial action at a challenging time for the NHS, with flu cases rising earlier than usual.

“Despite this, staff across the NHS are working extremely hard to maintain care and limit disruption,” he added.

But BMA leader Dr Tom Dolphin said keeping most services running would be “challenging”.

He said doctors had a legal right to strike and should not be “bullied or coerced” into working.

And he warned his members would only leave the picket line if there was a major emergency – such as a mass casualty event.

The latest walkout comes after Health Secretary Wes Streeting launched arguably his strongest attack on the BMA.

Addressing a conference of health managers this week, he called the union “morally reprehensible” and accused it of acting like a cartel, attempting to hold the public and government to ransom.

He said doctors had received generous pay rises over the past three years – worth nearly 30%, bringing average basic salaries to just over £54,000.

Talks between him and the union broke down last week after the BMA turned down a fresh offer to end the dispute.

Streeting has maintained throughout the year that he could not negotiate on pay, but he proposed a deal that would see out-of-pocket expenses like exam fees and membership fees covered, along with a boost in speciality training places.

But the BMA has argued that, despite the pay rises, resident doctors’ pay is still a fifth lower than it was in 2008, once inflation is taken into account.

The union has also warned doctors are struggling to find jobs at a key stage of their training – between years two and three when they start speciality training.

This year there were more than 30,000 applicants for 10,000 jobs at this stage, although some will have been doctors from abroad.

“We need a solution for the jobs crisis, that bottleneck for doctors who are out of permanent work or out of consistent work,” Dr Emma Runswick, deputy chair of the BMA Council, told the BBC.

“Then we need to be able to retain those doctors throughout their careers by paying them appropriately, and that means restoration of pay.”