In addition to being negative tests can only be 24 hours old. The rule will apply to both Danish citizens and foreigners, and it will be up to airlines to ensure passengers have been tested.
“That means that, as of January 9 at 5 pm, no airline will be allowed to fly to a Danish airport without having checked that all passengers onboard have tested negative,” transport minister Benny Engelbrecht told a news conference.
Domestic flights, as well as flights from Greenland and the Faroe islands will be exempt from the requirement, as will children under 12.
Border restrictions were also tightened for foreigners entering the country by land or sea, they would also need to produce a negative test and have a valid reason to travel, according to broadcaster DR.
The tighter restrictions were motivated by the circulation of reportedly more contagious variants of the novel coronavirus, specifically the ones discovered in the UK and South Africa.
The country's foreign ministry also issued new guidance on travel and said it was now advising against all travel abroad, replacing its previous guidance to avoid non-essential travel abroad.
“If you are considering travelling abroad, don't,” Foreign Minister Jeppe Kofod told reporters on Friday.
Last week health authorities reported they had confirmed 86 cases of the British variant in Denmark.
Responding to the threat of a more easily spread virus, Denmark on Tuesday announced even tighter measures on top of a partial lockdown in place since mid-December.
In addition to existing measures like working from home and the closure of schools, bars, restaurants and most shops, gatherings of more than five people were banned — down from 10 — and people were asked to keep two metres (six feet) apart, rather than one metre.
“Stay at home as much as you can, don't meet people outside your household, those close to you,” prime minister Mette Frederiksen said on Tuesday.
The new travel guidance as well as the restrictions are set to remain in place until January 17.