Freight drivers who are not British citizens and have been driving through Denmark in the last two weeks have been warned by the UK government that they will be turned away from the border.
The latest measures on Sunday were taken after people voiced their concerns over a new coronavirus strain that has spread from minks to humans in Denmark, reports Xinhua news agency.
British citizens can return from Denmark, but will have to isolate along with all members of their household for 14 days.
Cabin crew are also no longer exempt from the rules, which Ryanair described as a "bizarre and baseless" move, according to the BBC.
The new rules, which began at 4 a.m. on Sunday, follow a ban on non-British citizens coming to the UK from Denmark.
Five so-called clusters of coronavirus mutations derived from farmed mink in Denmark have now been found in 214 people.
Te most problematic "cluster 5" might have resistance to the antibodies with its "spike protein", the Danish Statens Serum Institut, a governmental public health and research institution under the Danish Ministry of Health, has said.
Passenger planes and ships carrying freight (as well as passengers) from Denmark will also not be allowed to dock at English ports, said the BBC.
The British Department for Transport (DfT) said the latest rules followed the release of "further information" from health officials in Denmark.
The travel ban and extra requirements will be reviewed after a week, the DfT said.
On November 5, a second lockdown came into force in England.