Doctors are being urged to call off further strike dates over the imposition of a controversial new contract, with some calling the decision "disappointing".
Junior doctors have announced they will stage additional full walkouts between 8am and 5pm on October 5, 6, 7, 10 and 11, November 14 to 18 and December 5 to 9.
The extra strike dates come on top of the five days of action set out on Wednesday, which will take place from September 12 to 16.
The Government and British Medical Association (BMA) remain at loggerheads over the contract weeks before it is brought in, which the Department for Health says will provide a seven-day NHS.
In the wake of the industrial action Prime Minister Theresa May accused the BMA of failing to put patients first and "playing politics" - something doctors have denied.
While the BMA says it is "absolutely behind" the decision for further action, the news of new strikes has not been welcomed by others.
A spokesman for the Academy of Medical Royal Colleges said they are "disappointed" at the prospect of further sustained industrial action.
"We are acutely aware that the NHS is under extreme pressure at the moment. Patient safety and quality of care must be the priority," he said.
"We know there are genuine concerns about the contract and working arrangements, but we do not consider the proposed strikes are proportionate.
"Five days of strike action, particularly at such short notice, will cause real problems for patients, the service and the profession."
Kathy McLean, executive medical director at NHS Improvement, also questioned the decision to strike and urged junior doctors to call it off.
She said: "Trusts across the country are working hard to ensure they are as prepared as possible in order to provide the best service to patients, who are likely to be severely inconvenienced by this industrial action.
"NHS Improvement will be working closely with NHS England to support them in this. I urge junior doctors to call off this action."
Mrs May said: "The BMA should be putting patients first - not playing politics."
BMA chairman Dr Mark Porter said: "I have to say it beggars belief that we can be accused of playing politics in this when the stated reason of the Government proceeding is that it was in their party manifesto. That, to me, is playing politics."
Six strikes have already taken place across England during the lengthy dispute, causing disruption to hundreds of thousands of patients who have had appointments and operations cancelled.
In May it looked as though a breakthrough had been reached in the dispute after both sides agreed to a new deal.
Then in July, the Government announced it would impose a new contract after junior doctors and medical students voted to reject the contract brokered between health leaders and the BMA.
The BMA said it will call off the strikes if the Government agrees to stop the imposition.
Fears have been raised for patient safety during the walkout, with Niall Dickson, chief executive of the General Medical Council, saying the strike represented a "serious escalation" of the dispute.
He added: "The first priority must be to protect patients from harm."
But Dr Porter sought to ease concerns, and said staff on duty will be more senior than those they might normally see and that patients "should not be concerned".
Dr Ellen McCourt, who chairs the BMA junior doctors' committee, said: "We want to resolve this dispute through talks, but in forcing through a contract that junior doctors have rejected and which they don't believe is good for their patients or themselves, the Government has left them with no other choice."