"This variant was detected in the UK on Friday 18 August, and has also been identified in Israel, Denmark and the US," the agency said in a statement.
"There is currently one confirmed case in the UK in an individual with no recent travel history, which suggests a degree of community transmission within the UK."
The new variant has a high number of mutations and is genomically distant from both its likely ancestor, BA.2, and currently circulating variants, the UKHSA said, adding that it had insufficient data to assess the potential immune response and the severity of the disease.
In late July, the BA.2.86 coronavirus variant was sequenced in Israel and Denmark, and then detected in the United States. A total of six cases of BA.2.86 have been detected in four countries, including the UK, by now. The World Health Organization (WHO) has stated it will actively monitor the highly mutated variant.