The World Health Organization has issued a stark warning to European nations, saying that relaxing Covid-19 measures could spark a "perfect storm" allowing cases to spiral, as seen in India.
New infections and deaths are soaring there, which experts have said can in part be blamed on mass gatherings in the nation of 1.3 billion people.
India's total number of Covid-19 cases has passed 18 million after another world record daily infection and death tally and as the government rejected reports of problems with its vaccine campaign.
The head of WHO Europe said countries should not make the mistake of relaxing restrictions too soon to avoid similar new waves of infection.
"When personal protective measures are being relaxed, when there are mass gatherings, when there are more contagious variants and the vaccination coverage is still low this can create a perfect storm in any country," Hans Kluge told reporters.
"It is very important to realise that the situation in India can happen anywhere."
The so-called Indian variant is sweeping the country, but the WHO has not yet confirmed whether it is more transmissible or more deadly than other strains of the virus.
Experts have said large gatherings - at sports matches or weddings, for example - are in part to blame for the explosion in cases.
Mr Kluge said European nations must keep in mind that "individual and collective public health and social measures remain dominant factors in shaping the pandemic's course".
He noted that while the number of new cases in Europe fell "significantly" last week for the first time in two months, "infection rates across the region remain extremely high".
He said vaccine programmes were on the rise in the European region, with 7% of the population now fully inoculated.
The WHO said this means that more people in Europe have now received the vaccine than the number of people who have been infected with the disease.
India reported 379,257 new Covid-19 cases and 3,645 deaths today, according to health ministry data.
It was the highest number of deaths reported in a single day in India since the start of the pandemic.
India's best hope to curb its second wave of Coivd-19 was to vaccinate its vast population, said experts, and yesterday it opened registrations for everyone above the age of 18 to be given jabs from Saturday.
But the country, which is one of the world's biggest producers of vaccines, does not have the stocks for the estimated 600 million people becoming eligible.
Many people who tried to sign up said they failed, complaining on social media that they could not get a slot or they simply could not get online to register as the website repeatedly crashed.
"Statistics indicate that far from crashing or performing slowly, the system is performing without any glitches," the government said in a statement last night.
The government said more than 8 million people had registered for the vaccinations, but it was not immediately clear how many had got slots.
About 9% of India's population have received one dose since the vaccination campaign began in January with healthworkers and then the elderly.
The second wave of infections has overwhelmed hospitals and crematoriums and prompted an increasingly urgent response from allies overseas sending equipment.
"India's Covid outbreak is a humanitarian crisis," US Democratic Senator Elizabeth Warren said on Twitter.
"I'm leading a letter to @moderna_tx, @pfizer, and @jnjnewsto find out what steps they’re taking to expand global access to their vaccines to save lives and prevent variants from spreading around the world."
Two planes from Russia, carrying 20 oxygen concentrators, 75 ventilators, 150 bedside monitors, and medicines totalling 22metric tonnes, arrived in the capital Delhi this morning.
The United States is sending supplies worth more than $100 million to India, including 1,000 oxygen cylinders, 15 million N95 masks and 1 million rapid diagnostic tests, the White House said in a statement.
The US also has redirected its own order of AstraZeneca manufacturing supplies to India, which will allow it to make over 20 million doses of Covid-19 vaccine, according to the White House.
Delhi is reporting one death from Covid-19 every four minutes and ambulances have been taking the bodies of virus victims to makeshift crematorium facilities in parks and carparks, where bodies burned on rows and rows of funeral pyres.
The US State Department issued a travel advisory warning against travel to India because of the pandemic and approved the voluntary departure of family members of US government employees in India.
Early modelling showed that the B.1.617 variant of the virus detected in India had a higher growth rate than other variants in the country, suggesting increased transmissibility.
The World Health Organization said in its weekly epidemiological update that India accounted for 38% of the 5.7 million cases reported worldwide to it last week.
