The UK is to send ventilators and oxygen to India to help it fight its devastating coronavirus crisis, with the US also offering assistance after Washington was accused of hoarding vaccines and of blocking the export of crucial supplies needed to produce doses.

The UK package includes 495 oxygen concentrators, which can extract oxygen from the air when hospital systems have run out, 120 non-invasive ventilators and 20 manual ventilators. It is expected to arrive in Delhi on Tuesday with further shipments later in the week.

India reported 349,691 new cases on Sunday, a record increase for the fourth consecutive day, and 2,767 people dead. Hospitals are running short of life-saving oxygen and patients are dying while they wait to see doctors.

The prime minister, Boris Johnson, said: “We stand side by side with India as a friend and partner […] I’m determined to make sure that the UK does everything it can to support the international community in the global fight against pandemic.”

International support for India is increasing amid warnings the country is on the brink of a humanitarian catastrophe. The US secretary of state, Anthony Blinken, has pledged to “rapidly deploy additional support to the people of India and India’s healthcare heroes” and Germany said on Sunday it was considering sending a mobile oxygen generator and other aid.

It is unclear if the US assistance will lead it to bow to growing pressure to lift export controls on raw materials intended to boost its vaccine supply that Indian vaccine manufacturers say are slowing down their ability to produce jabs.

It is feared that the official statistics and a death toll of 192,311 are underestimating the scale of the crisis as experts believe many people are not going to get tested, or lack access to healthcare.

Ashish Jha, the dean of the Brown University School of Public Health, said in an op-ed on Saturday in the Washington Post that India, a country of 1.3 billion people, was on the brink of a humanitarian catastrophe and called on Washington to send India oxygen and medicines and lift all export controls related to vaccines.

Jha also urged the Biden administration to share excess vaccines with India and other countries in crisis, pointing out that the US had an estimated 30m unused doses of the AstraZeneca vaccine that has not been authorised by US regulators. The calls were echoed by the author Salman Rushdie, who said: “The US has something like a vaccine glut. India is in dire straits. Please overturn this export ban ASAP.”

The unprecedented spread of the virus has overwhelmed hospitals in major cities, which continue to face severe shortages of beds and oxygen. “Every day it is the same scenario – we are left only with two hours of oxygen,” a doctor at Pentamed hospital in Delhi told the BBC. “This is the only request that we have, that we want oxygen.”

Narendra Modi’s government has faced mounting questions since the resurgence of the pandemic, which the health minister had declared in early March was in its “endgame”, over its lax safety measures and failure to prepare for a rise in cases. It emerged on Sunday that Indian officials were attempting to censor such criticism, after Twitter confirmed it had blocked dozens of critical tweets following a legal demand from New Delhi.

Modi, the prime minister, told the public in a radio address on Sunday to exercise caution and to get vaccinated. “Our spirits were high after successfully dealing with the first wave,” he said. “But this storm has shaken the nation.”

The government deployed special trains to move tanks of oxygen from steel plants to hospitals across the country in a bid to allow greater access to medical care. It said last week it planned to make vaccines available to all adults aged over 18 from 1 May, but the Serum Institute of India, which manufactures the AstraZeneca vaccine, has said it will not be able to meet its projected targets.

Adar Poonawalla, the chief executive, appealed to President Biden earlier this month to lift restrictions on supplies needed for production. “I humbly request you to lift the embargo of raw material exports out of the US so that vaccine production can ramp up. Your administration has the details,” he said on Twitter.

The SII also manufactures vaccines for the international Covax programme intended to help the developing world, which is set to deliver only one in five of the doses it had estimated it would supply by May.

When asked about the export ban on Thursday, state department spokesperson Ned Price said the US had “a special responsibility to the American people”.

India, which has embarked on the world’s largest vaccination drive, has administered more than 140m doses of vaccine. So far, 8.47% of people have received one dose, and 1.55% are fully vaccinated.

The White House press secretary, Jen Psaki, on Friday said US and Indian officials were working to find ways to help address the crisis, but did not specify a timeframe. She said the US had already provided India with $1.4bn in health assistance, emergency relief supplies, pandemic training for Indian state and local health officials, and ventilators.

Milind Deora, a member of parliament from Mumbai, one of the worst affected cities, said the US was “undermining the strategic Indo-US partnership”.

Raja Mohan, the director of the Institute of South Asian Studies atthe National University of Singapore, said the episode was “a jarring note” but that it was unlikely to have a lasting impact on US India relations. “If the package comes through I’m sure these sort of controversies will be forgotten,” he said.

(With inputs from agencies)