In his first comment on the unprecedented public protests against his stringent zero-Covid policy, Chinese President Xi Jinping told EU President Charles Michel that they were carried by "mainly students" who were "frustrated" after three years of the pandemic, a media report said on Friday.

Xi held talks with Michel in Beijing on Thursday. In his talks, Michel "pleaded for use of vaccines and then raised the question of China's measures and government measures," a senior official said, the Hong Kong-based South China Morning Post newspaper reported from Brussels.

"And the response we got from the President was explaining why there were protests, claiming that after three years of Covid he had an issue because people were frustrated. It was mainly students or teenagers in university," they added.

European officials say Xi's comments during a meeting with Michel signal that he is ready to loosen controls further.

The Chinese leader is also reported to have said that the dominant Omicron strain is "less lethal", but expressed concern about vaccinating the elderly, the Post reported.

This is the first time Xi commented on the public protests, which were reported to have rattled his government. Following this, security has been stepped up in all main cities in China.

In a rare public outburst in China, thousands of people staged protests in various cities opposing the strictly followed zero-Covid policy under cities as well as scores of apartments were being locked down by officials to stop the coronavirus from spreading.

Protestors also called Xi, who was last month re-elected for an unprecedented third term to step down. The slogans called on the ruling Communist Party of China (CPC) to quit power.

The zero-Covid policy which has been followed by China during the past three years intensified in the last few months as the Omicron variant spread fast in several cities, including Beijing.

Publicly, China has not acknowledged the protests, while the coverage has been heavily censored in the official media.

EU officials who were present during Xi-Michel talks see the Chinese President's broader remarks about pandemic controls as a signal that he was ready to further loosen tight restrictions, which have left tens of millions of people under lockdown across the country, the report said.

There is no official reaction to the report in Beijing.Reports in the official media here in the last few days said the controls are being eased in many cities.

Xi told Michel that the dominant strain of Covid-19 in China is "now mainly Omicron, and Delta before that was much more lethal".

It said a second EU official stated that the Chinese leadership had intimated that it would try to push vaccinations in response to the unrest, with Michel sharing with Xi and his most senior underlings the European experience of rolling out mass vaccinations.

Xi told Michel that China had "high rates of vaccination, except for elderly people, which is a challenge", they said.

"My sense was that this [exchange] was something that was informative. I had a feeling that China would on its side be increasingly looking to incentivise its citizens to be vaccinated, to follow a tiny bit of the European experience," the second official said.

In China, only 68.7 per cent of people over 60 have had three doses of a Covid-19 vaccine, official figures show. For those aged 80 and over, only 40.4 per cent have had a booster dose.

China so far used locally produced vaccines and not pushed hard for vaccinating the elders, which experts say due to lack of confidence, while the world over elders have been vaccinated first for Covid.

China has yet to license the use of Western vaccines for the general public, but during a meeting with German Chancellor Olaf Scholz last month, Xi signalled that foreigners living in the country would be approved to take the BioNTech/Pfizer vaccine.

BioNTech filed for a Chinese licence for its mRNA vaccines last year, but it has yet to be granted.