Thousands of patients are expecting to face further disruption to NHS services as junior doctors take to picket lines once more in their ongoing dispute with the Government.
Figures from NHS England show that more than 5,100 procedures and operations have been postponed as a result of a 48-hour industrial action from 8am today.
Overall almost 25,000 procedures have been cancelled as a result of ongoing strike action by junior doctors in England.
The walkout, which will still see junior doctors provide emergency care cover, is the fourth round of industrial action taken by the British Medical Association (BMA) in the row over a new contract for junior doctors.
Dr Anne Rainsberry, national incident director for NHS England, said: "We've already seen that a 48-hour strike puts considerably more pressure on the NHS and it's deeply regrettable that thousands of patients are still facing disruption because of this recurring action.
"As always, the safety and care of patients is our number one priority and everythisng possible is being done to make sure patients will still be able to access urgent and emergency services.
"Following closely on from the four-day Easter break, this will be a difficult period especially over the course of the second day. Consequently we have redoubled our planning efforts and will be closely monitoring events to make sure we can respond to any rising pressures."
A Department of Health spokeswoman added: "This strike is irresponsible and disproportionate, and with almost 25,000 operations cancelled so far, it is patients who are suffering.
"If the BMA had agreed to negotiate on Saturday pay, as they promised to do through Acas in November, we'd have a negotiated agreement by now. We ask doctors to look at the detail of the contract and call on the BMA to cancel their plans to escalate strike action even further."
The BMA has called on the Government to resume negotiations and end the dispute through talks.
Dr Johann Malawana, chairman of the BMA's junior doctor committee, said: "We deeply regret any disruption this action will cause to patients, but it is because we believe this contract would be bad for the delivery of patient care in the long term that we are taking this action.
"By imposing a contract that junior doctors have no confidence in and refusing to re-enter talks with the BMA, the Government has left us with no choice.
"We want a contract that is fair for all junior doctors - not one of which the Government has admitted will disadvantage women - and ensures that they feel valued and motivated so that the NHS can retain the GPs and hospital doctors of the future.
"By pursuing its current course, the Government risks alienating a generation of doctors. If it continues to ignore junior doctors' concerns, at a time when their morale is already at rock-bottom, doctors may vote with their feet which will clearly affect the long-term future of the NHS and the care it provides.
"Responsibility for industrial action now lies entirely with the Government. They must start listening and resume negotiations on a properly funded junior doctor's contract to protect the future of patient care and the NHS."
Junior doctors are objecting to a new contract in England which the Government says will create a truly seven-day service.
They are currently paid more for working unsocial hours at night or at the weekend.
But under the proposed new contracts, the Saturday day shift will be paid at a normal rate in return for a rise in basic pay.
The dispute has become increasingly fraught and junior doctors have two strikes planned for this month.
Strikes planned for Tuesday, April 26, and Wednesday, April 27, will see the full withdrawal of labour by junior doctors - everyone up to consultant level - between the hours of 8am and 5pm on both days.
On Monday it emerged that Health Secretary Jeremy Hunt is facing a second legal challenge to try to block the imposition of the contract, with the threat of action from NHS staff campaign group Just Health.
The BMA announced last week it was launching a judicial review challenging the lawfulness of the imposition of the contract.