Bulgaria has banned UK travelers from entering the country due to concerns about the growing number of coronavirus cases in Britain.

The decision was made just days before Bulgaria was due to move to the UK's green travel list at 4am on Monday - meaning quarantine-free travel for passengers arriving in the UK from Bulgaria.

The south-east European nation has put the UK on its high risk "red zone list" along with Cyprus, Spain, Fiji and Kuwait.

It comes as the UK reported more than 50,000 new COVID-19 cases in the latest 24-hour period, the highest number since mid-January.

Aviation analyst Alex Macheras indicated that Bulgaria may simply be the first of many countries to refuse entry to British travelers as coronavirus rate continue to rise.

He said: "Most countries around the world implement travel bans on other countries based on COVID-19 numbers, rates or variants."

"While (health secretary) Sajid Javid may be comfortable with 100,000+ daily COVID-19 delta (variant) cases, other countries will not be so understanding."

(With input from agencies)