COVID-19 cases are spiking alarmingly across Europe only a few months after the continent eased travel restrictions, and the World Health Organization (WHO) now warns of a "very serious situation" facing Europeans.

WHO pointed out that this second wave has been so severe the total number of weekly cases now exceeds what were previously the worst numbers back in March. It said the upsurge reveals alarming rates of transmission across Europe. The case surge has also been partly due to wider testing in many European nations.

"Weekly cases have now exceeded those reported when the pandemic first peaked in Europe in March," said WHO regional director Hans Kluge. "Last week, the region's weekly tally exceeded 300,000 patients."

He said more than half the European countries have reported an increase of more than 10% in new cases over the past two weeks. Of this total, seven countries have seen newly reported cases increase more than two-fold in the same period.

"In the spring and early summer we were able to see the impact of strict lockdown measures," he noted. "Our efforts, our sacrifices, paid off. In June cases hit an all-time low. The September case numbers, however, should serve as a wake-up call for all of us," he said.

COVID-19 hospitalizations have risen in recent days in large French cities such as Paris, Bordeaux and Marseille while new infection numbers are swiftly climbing. A French record was set over the weekend with more than 10,000 new cases in a single day. The number of people in intensive care jumped 25 percent in the past week.

Cases in Germany, Italy, Spain and the United Kingdom are rising fast. More than 42,000 people have died from COVID-19 in the UK, the highest toll in Europe and fifth-largest number in the world.

As in the United States, most of the new cases are among people younger than 50 years old. Kluge said most of the new cases in the first week of September were among 25- to 49-year-olds.

Kluge rues the pandemic has taken so much from Europe, citing the 4.9 million confirmed COVID-19 cases in Europe and more than 226,000 deaths.

"And this tells only part of the story," he said. "The impact on our mental health, economies, livelihoods and society has been monumental."

This is the second time in two weeks WHO has warned of the grave coronavirus situation in Europe. As September began, WHO said the number of new COVID-19 cases in Europe jumped 5.6 percent to more than four million cases from June 7 to the week ending August 23.

This total represents a six percent hike compared to the previous week, and an increase of 72 percent compared to the week ending June 7, which saw the lowest number of infections per week.

More than half of the new cases in the week ending August 23 came from four countries: Spain (21 percent), Russia (16 percent), France (10 percent), and Ukraine (6 percent).

The 14-day case notification rate for the EU, the European Economic Area (EEA) and the United Kingdom stood at 46 per 100,000 population as of August 26, said the European Center for Disease Prevention and Control (ECDC).