Experiments with a mutant Covid strain are said to have been carried out by Chinese scientists, despite concerns the research could spark another pandemic.

The mutant strain is thought to be 100 per cent lethal in mice and spreads through the body in a "unique way".

The Covid-like virus was cloned by scientists in Beijing, who are linked to the Chinese military, and used it to infect mice.

It has been claimed that the experiment saw the mice engineered to express a protein found in people, in a bid to see how the virus might react in humans.

Researchers were surprised to see how the virus multiplies and spreads after finding high levels of viral load in the mice's brains and eyes.

An unpublished paper warned the finding "underscores a spillover risk of GX_P2V into humans".

Professor Francois Balloux, an infectious disease expert based at University College London, wrote on social media: "It's a terrible study, scientifically totally pointless.

"I can see nothing of vague interest that could be learned from force-infecting a weird breed of humanized mice with a random virus. Conversely, I could see how such stuff might go wrong..."

The virus was reportedly discovered in 2017, before the Covid outbreak.

According to the study, it was discovered in Malaysia in pangolins - mammals which commonly harbour coronaviruses and were suspected to be the intermediate host that passed Covid from bats to humans.