An autopsy confirmed sexual assault and, in a petition to the court, the victim's parents said they suspected their daughter was gang-raped.

One man, who worked at the hospital helping people navigate busy queues, has been detained.

However, Kolkata's police were accused by an angry public of mishandling the case and the city's High Court transferred the investigation to India's top Central Bureau of Investigation to "inspire public confidence".

Those in government hospitals across several states on Monday halted elective services "indefinitely", with multiple medical unions in both government and private systems backing the strikes.

The Indian Medical Association (IMA) escalated protests on Saturday morning with a 24-hour "nationwide withdrawal of services", and the suspension of all non-essential procedures.

"We ask for the understanding and support of the nation in this struggle for justice for its doctors and daughters," IMA chief R.V. Asokan said in a statement ahead of the strike.

The IMA called the killing "barbaric".

"The 36-hour duty shift that the victim was in and the lack of safe spaces to rest... warrant a thorough overhaul of the working and living conditions of the resident doctors," the IMA said in a statement.

Doctors are demanding the implementation of the Central Protection Act, a bill to protect healthcare workers from violence.

"There is a lack of proper infrastructure," said 29-year-old Akanksha Tyagi, a resident at the Lady Hardinge Medical College in New Delhi who took part in one of the multiple protests around the country.

"After working for 24-36 hours at a stretch, there's no proper place for us to rest," she said.

The strike disrupted outpatient services.

At Delhi's Ram Manohar Lohia public hospital, one of the city's busiest, many who had turned up for their scheduled appointments were turned away.

Shivdev Kumar, 50, had travelled over 20 kilometres (12 miles) with the tuberculosis reports of his daughter, only to find the doctor's room locked.

"I had no idea, otherwise I would not have such a long way," he said.