The United States joined nations imposing Covid-19 tests on travellers from China after Beijing dropped foreign travel curbs despite surging cases, but the EU's health agency said Thursday such measures were not warranted in the bloc.

The head of the World Health Organization, however, said the restrictions some countries were introducing were "understandable" given the lack of information out of Beijing.

Hospitals across China have been overwhelmed by an explosion of infections following Beijing's decision to lift strict rules that had largely kept the virus at bay but tanked the economy and sparked widespread protests.

China said this week it would end mandatory quarantine on arrival, prompting many Chinese to make plans to travel abroad.

In response, the United States and several other countries announced they would require negative Covid-19 tests for all travellers from mainland China.

"The recent rapid increase in Covid-19 transmission in China increases the potential for new variants emerging," a senior US health official told reporters.

Beijing has provided only limited information to global databases about variants circulating in China, the official said, and its testing and reporting on new cases have diminished.

The US move came after Italy, Japan, India and Malaysia announced their own measures in a bid to avoid importing new variants from China.

WHO calls for data

The European Union's health agency said Thursday it believed the EU-wide introduction of mandatory Covid-19 screenings for travellers from China was currently "unjustified".

The European Centre for Disease Prevention and Control (ECDC) pointed to the "higher population immunity in the EU/EEA, as well as the prior emergence and subsequent replacement of variants currently circulating in China".

But in a series of tweets, WHO chief Tedros Adhanom Ghebreyesus renewed his appeal to China to be more forthcoming on the pandemic situation in the country.

"In order to make a comprehensive risk assessment of the Covid-19 situation on the ground in China, WHO needs more detailed information," Tedros wrote.

"In the absence of comprehensive information from China, it is understandable that countries around the world are acting in ways that they believe may protect their populations."

Already on December 21, Tedros had expressed concern about the situation in China, calling for detailed data on disease severity, hospital admissions and intensive care requirements.

'Smears'

Following the announcements by some countries of travel restrictions, Beijing has hit out against "smears with ulterior motives" by the Western media.

"Over the past three years we have effectively responded to five waves of global outbreaks... winning precious time for the development of vaccines and medicines," foreign ministry spokesman Wang Wenbin told a briefing Thursday.

China still does not allow foreign visitors, however, with tourist and student visas suspended.

Those eligible to arrive in China must also provide a negative PCR test taken no more than 48 hours before entering the country.

The lifting of mandatory quarantine sparked a surge in interest in overseas travel by Chinese citizens, who have been largely confined to their country since Beijing pulled up the drawbridge in March 2020.

At Beijing's Capital International Airport, one passenger bound for Budapest told AFP: "It's good to see our borders opening."

On the restrictions introduced by some countries, he said: "Every country has their own policies. We just follow them and still go where we need to go."

But one 22-year-old man surnamed Hu denounced the introduction by some countries as unnecessary and "a bit discriminatory".

"Our Covid-19 policy for international arrivals is applied equally," he said. "Why do other countries need to give arrivals from China special treatment?"

Bodies piling up

On the front lines of China's Covid-19 wave, hospitals are battling surging cases that have hit the elderly and vulnerable hardest.

AFP reporters saw masked patients on stretchers being unloaded from several ambulances at a major hospital in Shanghai on Thursday.

They overheard a patient arguing with hospital staff after waiting four hours to collect medicine.

Two hospitals in Tianjin, around 140 kilometres southeast of Beijing, were also overwhelmed with patients and doctors were being asked to work even if infected.

"It's a four-hour wait to see a doctor," staff could be heard telling an elderly man who said he had Covid-19.

"There are 300 people in front of you."

China's National Health Commission said last week it would no longer release an official daily Covid-19 death toll.

A national disease control body added just over 5,000 new local cases and one death on Thursday but, with the end of mass testing and the narrowing of criteria for Covid deaths, those numbers are no longer believed to reflect reality.