Authorities said they have launched an inquiry but denied reports that a lack of oxygen had caused the deaths at the Baba Raghav Das Hospital in Gorakhpur district in Uttar Pradesh state, which is ruled by Prime Minister Narendra Modi's Bharatiya Janata Party.
Indian media said 30 children died on Thursday and Friday after oxygen supply was disrupted in wards housing the sick, allegedly because the suppliers' bills were not paid.
"We have launched an inquiry and a preliminary report should be out today. Yes, sixty patients have died at the hospital in the last five days but we don't think it's linked to reports of oxygen shortage," Anil Kumar, Gorakhpur's divisional commissioner told AFP.
A statement issued by the office of state chief minister Yogi Adityanath, which has ordered the inquiry, said that all 60 deaths had occurred at the hospital's paediatric ward over a five-day period starting Monday.
Twenty-three children died on Thursday, when, according to the statement, "the pressure of the liquid oxygen supply became low and 52 reserve oxygen cylinders were pressed into service".
The Hindustan Times newspaper on Saturday described chaotic scenes at the hospital as oxygen supply was disrupted.
"Even as 90 jumbo oxygen cylinders were pressed into service to maintain the supply on Friday, the hospital ran out of oxygen around 1.00am," it said.
"All hell broke loose," the report added.
"What followed was complete chaos as panic-stricken relatives of patients ran for help, and with the support of hospital staff tried to maintain supply of oxygen... using artificial manual breathing bags.
"However several patients started collapsing due to inadequate supply," it added.
The region is one of India's poorest and registers hundreds of child deaths each year from Japanese Encephalitis and Acute Encephalitis Syndrome, which is rife in parts of eastern and northern India.
"We will be getting more liquid oxygen cylinders tonight or tomorrow, and have also cleared the dues of the supplier," district official Kumar told AFP.
He added that the deaths "could be (due to) natural (causes), as many patients admitted at the hospital are serious".
India's Nobel Peace laureate Kailash Satyarthi, a campaigner for children's rights, described the deaths as "a massacre" on Twitter.
"Thirty kids died in hospital without oxygen. This is not a tragedy. It's a massacre. Is this what 70 years of freedom means for our children?," he said.
