NEW DELHI, April 28 (Reuters) - India's toll from the coronavirus surged past 200,000 on Wednesday (Apr 28), the country's deadliest day yet, as shortages of oxygen, medical supplies and hospital staff members compounded a record number of new infections.

The second wave of infections has seen at least 300,000 people test positive each day for the past week, overwhelming healthcare facilities and crematoriums and driving an increasingly urgent international response.

The last 24 hours brought 360,960 new cases for the world's largest single-day total, taking India's tally of infections to nearly 18 million. It was also the deadliest day so far, with 3,293 fatalities taking the toll to 201,187.

Experts believe the official tally vastly underestimates the actual toll in a nation of 1.3 billion, however.

In the capital, New Delhi, ambulances lined up for hours to take COVID-19 victims to makeshift crematorium facilities in parks and parking lots, where bodies burned on rows of funeral pyres.

Coronavirus sufferers, many struggling for breath, flocked to a Sikh temple on the city's outskirts, hoping to secure some of its limited supplies of oxygen.

Hospitals in and around the Indian capital said oxygen remains scarce, despite commitments to step up supplies.

"We spend the day lowering oxygen levels on our ventilators and other devices as our tanks show alarmingly dipping levels," Dr Devlina Chakravarty, the managing director of the Artemis hospital in the suburb of Gurgaon, wrote in the Times of India newspaper.

"We make hundreds of calls and send messages every day to get our daily quota of oxygen."

Delhi Chief Minister Arvind Kejrilwal said people were falling sick more severely and for longer periods, stacking up the pressure.

"The current wave is particularly dangerous," he said.

"It is supremely contagious and those who are contracting it are not able to recover as swiftly. In these conditions, intensive care wards are in great demand."