The government has reintroduced red list restrictions on arrivals from South Africa, Botswana, Lesotho, Eswatini, Zimbabwe and Namibia with immediate effect.
The move comes in response to the discovery of a new variant of Covid-19.
Variant B.1.1.529 has been declared a “variant under investigation” by the UK Health Security Agency (UKHSA).
Officials said the variant includes a large number of spike protein mutations as well as mutations in other parts of the viral genome.
These are “potentially biologically significant mutations which may change the behaviour of the virus with regards to vaccines, treatments and transmissibility”.
More investigation is required, the government said in a statement.
As a result of the decision, British and Irish citizens, or those with residence rights, arriving to England from countries on the red list must book a managed quarantine hotel in advance.
The package will include a managed quarantine hotel, quarantine transport and a test package for Covid-19 on day two and day two of quarantine.
From midday, non-UK and Irish residents who have been in these countries in the previous ten days will be refused entry.
This does not apply to those who have stayed airside and only transited through any of these countries while changing flights.
A temporary ban on commercial and private planes travelling from the six countries will also come into force at midday on Friday until early on Sunday.
No cases of the new variant have been identified in the UK to date.
Transport secretary, Grant Shapps, said: “We’ve always maintained public safety is our number one priority, which is why we’ve kept in place measures which allow us to protect the UK from new variants.
“We’re taking this early precautionary action now to protect the progress made across the country, and will continue to keep a close eye on the situation as we continue into the winter.”
Commenting on the news, Rory Boland, Which? Travel editor, said the situation remained fluid.
He added: “This worrying news is a reminder that travel is not back to normal.
“The pandemic continues to disrupt passengers’ travel plans, often with very little notice.
“As all flights are being suspended to these countries, all passengers will be entitled to a full refund for the holiday or flight, so long as they booked with a UK or EU carrier, or with any carrier due to depart from the UK or EU.
“Getting a refund for accommodation can be more difficult, and is dependent on the policy of the property.
“We have seen restrictions change in several countries over recent days and refunds are not always guaranteed.
“It is vital that travellers choose holiday providers with good, flexible booking policies in case your trip can’t go ahead.”