The United States and a WHO expert demanded more data from Beijing on late Saturday about the origins of the coronavirus pandemic, after a WHO mission to China struggled to make headway.
A team of World Health Organization experts and Chinese counterparts visited key sites around the city of Wuhan, where Covid cases were first detected, but said they had not been able to shed light on the nature of early transmissions.
US national security advisor Jake Sullivan said his country had "deep concerns" about the early findings of the investigation.
Peter Ben Embarek, who led the WHO mission, told AFP in an interview his team had asked for more data, adding: "There is a mix of frustration but also a mix of realistic expectations in terms of what is feasible under which time frame."
Experts believe the disease — which has killed nearly 2.4 million people worldwide — originated in bats and could have been transmitted to humans via another mammal.
But while the virus was first discovered in Wuhan in December 2019, it remains unclear if that is when and where the contagion actually began.
The fallout came as Europe's death toll topped 800,000 and concerns over coronavirus variants that first emerged in Britain and South Africa forced ever tighter border controls.
'Nobody Wants This'
Germany is ramping up its border security, closing its frontiers with the Czech Republic and parts of Austria.
"I must cross the border before midnight," professional driver Ludvik Boucek told AFP on Saturday afternoon as he washed his truck at a service area at the western Czech crossing of Rozvadov.
"I'm glad the company dispatcher told me about the closure. I hadn't heard anything about it."
Portugal, among the world's hardest-hit nations, on Saturday extended the suspension of flights from Britain and Brazil to March 1.
On Friday, the government in Lisbon extended border controls with neighbouring Spain until March 1.
The pandemic has also hit international sporting events with the Australian Open tennis tournament in Melbourne forced to continue without spectators as Victoria state enters its third lockdown since the pandemic began.
"The feeling is completely different — nobody wants this," said Spanish great Rafa Nadal, referring to the 15,000 empty seats that faced him at Rod Laver Arena.
While the tennis has been able to continue, Brazilian officials have been forced to cancel Rio de Janeiro's famed carnival.
The city would normally be enjoying the booming beats, glittering floats and glamorous dancers, but instead the "Sambadrome" is this year hosting a Covid-19 vaccination drive.
"Instead of a party, we're mourning our dead," Nilcemar Nogueira, founder of Rio's Samba Museum, told AFP.
The virus toll in Brazil stands at over 237,000, the second-highest number of deaths worldwide after the United States.
In neighbouring Peru, health minister Pilar Mazzeti resigned on Friday as a scandal grows over claims that former President Martin Vizcarra was vaccinated before the jab was available to the public.
Peru only began its immunisation programme on Tuesday, two days after receiving 300,000 vaccine doses from state-owned Chinese company Sinopharm.
But the Peru 21 newspaper reported on Thursday that Vizcarra had been vaccinated in secret in October, just weeks before he was impeached and removed from office on charges that he was "morally incompetent".
Meanwhile in Cyprus, police used water cannon and tear gas in rare clashes with protesters as hundreds demonstrated against government corruption and coronavirus restrictions.