Denmark's health authorities said the country had seen a "concerning" jump to 183 confirmed cases of the Omicron variant of Covid-19.

The number represented a tripling of confirmed cases in 48 hours, from 18 confirmed and 42 suspected cases on Friday, according to data from the SSI public health institute.

The European Centre for Disease Prevention and Control (ECDC) had previously tallied just 182 cases across all of the European Union, plus Norway and Iceland.

Denmark is one of Europe's most advanced countries in sequencing of coronavirus variants.

It often detects more cases more quickly than its neighbours - which does not necessarily indicate higher rates of infection.

SSI chief said the increase in Omicron cases was nevertheless "concerning", adding that "there are now chains of infection where the variant is found in people who have not travelled abroad or been in contact with travellers".

Latest coronavirus stories

Also today, the ECDC said Omicron had been reported in 17 countries in its region.

"The majority of confirmed cases have a history of travel to countries in Africa, with some having taken connecting flights at other locations between Africa and Europe," the ECDC said on its website before the Danish announcement.

Nevertheless, "several EU/EEA countries (Belgium, Germany, Spain) detected cases without an epidemiological link to areas where community transmission of the Omicron variant is documented or presumed," it added.

"This indicates that undetected community transmission could be ongoing in these countries."

Britain's health security agency reported 86 new cases of the variant, taking the total number identified so far to 246.

Omicron variant found in at least 15 US states - CDC chief

The Omicron variant has been found in about 15 US states so far, but the Delta variant remains the majority of Covid-19 cases nationwide, the head of the US Centers for Disease Control and Prevention has said.

"We know we have several dozen cases and we're following them closely. And we are every day hearing about more and more probable cases so that number is likely to rise," CDC Director Dr Rochelle Walensky told ABC News in an interview, adding more data is still needed.

At least 15 states have reported Omicron cases: California, Colorado, Connecticut, Hawaii, Maryland, Massachusetts, Minnesota, Missouri, Nebraska, New Jersey, New York, Pennsylvania, Utah, Washington and Wisconsin, according to a Reuters tally.

Louisiana has also reported a probable case, while the person reported in New Jersey had also previously traveled to Georgia, which also reported the positive test.

Still, Dr Walensky said Delta accounted for most cases in the United States and as vaccines are known to protect against hospitalisation and death, health officials hope they will blunt the impact of Omicron as well.

She said that of the 90,000 to 100,000 cases a day, 99.9% oft hem are the Delta variant.

"We have an issue right now in the United States about Delta," Walensky told ABC's This Week

Covid cases reported on Norwegian Cruise ship

Ten cases of Covid-19 have been detected on a cruise ship with over 3,000 passengers, which is set to dock in New Orleans, the Louisiana Department of Health has said.

The cruise ship Norwegian Breakaway, owned by Norwegian Cruise Line Holdings Ltd, departed New Orleans on aweek long cruise on 28 November and had stops in Belize, Honduras and Mexico, the health agency said.

"NCL has been adhering to appropriate quarantine and isolation protocols," the department said in a tweet.

The ship is set to reach New Orleans this morning, according to its itinerary.

Everyone on board will be tested for Covid-19 before leaving and will be provided with post-exposure and quarantine public health guidance by the US Centers for Disease Control and Prevention (CDC).

People who test positive for Covid-19 will either travel to their homes or self-isolate according to CDC guidelines, the health agency said.

India reports highest Covid-19 fatalities since July as states update tallies

India has reported its highest single-day Covid-19 deaths since July after two states revised their death tolls.

The eastern state of Bihar added 2,426 unrecorded deaths while the southern state of Kerala added 263 deaths to their tallies, a federal health ministry spokesperson said.

The revised figures took single-day deaths to 2,796, the highest since 21 July, according to a Reuters tally.

A devastating second wave in March and April this year saw thousands of deaths and millions affected.Indian states have continued to add unreported Covid-19 deaths in recent months, lending weight to some medical experts' opinions that such deaths are much higher than the reported number of 473,326.