The UK government on Thursday announced the removal of Croatia, Trinidad and Tobago and Austria from countries and territories in its travel corridors list.

Passengers arriving from those countries from Saturday 22 August will need to self-isolate for two weeks following a "a significant increase in confirmed cases."

"Data from the Joint Biosecurity Centre and Public Health England has indicated a significant change in both the level and pace of confirmed cases of coronavirus (COVID-19) in all 3 destinations, leading to ministers removing these destinations from the current list of travel corridors," a statement from the government read in part.

According to the statement, the weekly incidence for Croatia saw a 164 percent increase between August 12-19, while there had been a "consistent increase" in the weekly incidence rate of COVID-19 in Trinidad and Tobago in the last one month.

It also said that the weekly incidence for Austria saw a 93 percent increase between August 13-20.

People who violate the self-isolation directive face fines of up to £1,000 in England, Wales and Northern Ireland, while in Scotland it is £480, according to the BBC.

Portugal, meanwhile, was added to the government’s travel corridor list following a decrease in confirmed cases of coronavirus.

"Passengers arriving in England from Portugal at or after 4am on Saturday 22 August will not need to self-isolate, so long as they haven’t been in or transited through any other non-exempt countries in the 14 days preceding their arrival."

The UK government re-imposed quarantine restrictions from late July on a number of countries after initially relaxing blanket restrictions on people coming into the country at the beginning of July.

Some of the countries affected were: Spain, Luxembourg, Belgium, Andorra, the Bahamas, France, the Netherlands, Malta and Monaco.

(With input from agencies)