Junior doctors in England have begun their first 48-hour strike as part of their ongoing protest over threats to impose a new contract.

The 38,000 members of the British Medical Association are providing emergency care only until 8am on Friday.

More than 5,000 operations are expected to be cancelled over the following two days.

Outpatient clinics are also likely to be affected as consultants rearrange their work to cover gaps left by striking medics.

Anne Rainsberry, national incident director for NHS England, said hospitals will make sure patients are safe.

"There are difficult days ahead for the NHS. We have been working closely with hospitals to ensure they have robust plans in place," she said.

"It's a very fluid situation. Hospitals have been making decisions based on clinical priority."

This is the third strike in the dispute over a new contract, but the first time they have walked out for two consecutive days.

The Department of Health wants changes made to unsocial hours payments and working hours to ensure more junior doctors are available at weekends.

But the British Medical Association warns doctors will work longer for less.

Both sides claim to be acting in the interests of patient safety.

Nadia Masood, who is training to become a consultant anaesthetist, told Sky News the new contract would make her so tired that she would struggle to calculate drug doses.

"Calculations that I do in my job are critical. If we get a decimal point wrong, that can be fatal," she said.

"We work every day to make sure that doesn't happen.

"If we are tired then the chances of making those mistakes go up. We're only human like everyone else."

The two sides failed to reach an agreement in talks lasting several months and Health Secretary Jeremy Hunt has said he will now impose the contract.

One-year-old Jenson Purnell was due to have major surgery to rebuild his urethra or urine tube, but the operation has been cancelled.

His mum, Zoe, who works for the NHS, said she blamed the Government for the strike.

"For a child to have a general anaesthetic is a big thing, especially for one as young as Jenson," she said.

"Emotionally that really upsets me. I have to build myself up again for when his date does come around."

A Department of Health spokesman said the action was "irresponsible and unjustified".

"The new contract, 90% of which was agreed with the BMA and endorsed by senior NHS leaders, is a very good deal for doctors and the NHS."

Further 48-hour strikes are planned from 8am on 6 April and 8am on 26 April.