The World Health Organisation is monitoring a new coronavirus variant known as "Mu", which was first identified in Colombia in January, the UN health body said on Tuesday in its weekly pandemic bulletin.
WHO has classified Mu as a "variant of interest," saying it has mutations that indicate a risk of resistance to vaccines.
"The Mu variant has a constellation of mutations that indicate potential properties of immune escape," the bulletin said.
It stressed that further studies were needed to better understand it.
While the global prevalence of Mu is low, the new strain is gaining ground in South America, WHO said.
"Although the global prevalence of the Mu variant among sequenced cases has declined and is currently below 0.1%, the prevalence in Colombia (39%) and Ecuador (13%) has consistently increased."
There is widespread concern over the emergence of new virus mutations as infection rates are soaring again, fueled by the highly contagious Delta variant.
All viruses, including SARS-CoV-2 that causes COVID-19, mutate over time and most mutations have little or no effect on the properties of the virus.
But certain mutations can impact the properties of a virus and influence how easily it spreads, the severity of the disease it causes, and its resistance to vaccines, drugs and other countermeasures.
The WHO currently identifies four coronavirus variants of concern, including Alpha, which is present in 193 countries, and Delta, present in 170 countries.
Five variants, including Mu, are to be monitored.