Foreign travellers arriving to Sweden were as of Saturday to present a negative coronavirus test no older than 48 hours in order to enter the country.
Prime Minister Stefan Lofven and other cabinet members announced the measure earlier this week.
It will run until March 31 and applies to people over the age of 18.
The government said it was acting on concerns raised by the Swedish Public Health Agency regarding the spread of new, more contagious variants of the coronavirus, including a strain initially detected in Britain.
Exemptions included urgent family reasons, employees in the transport sector or people who commute across borders for work. People in the last category were advised to test themselves on a weekly basis.
Swedish nationals or those with residency status in Sweden were advised to be tested before their arrival - or to be tested the same day they arrived. They should self-isolate for seven days and take a second test during that period, according to the government's advice.
Separately, the government extended an entry ban from Britain, Denmark and Norway until March 31.
The decision centered on "uncertainty" regarding the spread of the more contagious strains of the coronavirus in the three countries, Mikael Damberg, minister for home affairs, told Swedish Radio.
Sweden, a country of 10.3 million, had as of Friday registered over 588,000 cases and 12,115 deaths since the pandemic began.