OSLO (Reuters) – Norway will close its borders to all but essential visitors, Prime Minister Erna Solberg said on Wednesday, tightening further some of the toughest travel restrictions in Europe.

“In practice, the border will be closed to anyone not living in Norway,” Solberg told a news conference.

While exceptions will apply to a few groups, including health workers from some countries, most migrant labor will be prevented from coming, she said.

“What we see is that the mutated virus has spread significantly in many countries that do not monitor the extent of mutations in the same way as Norway, Denmark and Britain do,” said Solberg of the reasons why the latest measures were introduced.

The non-EU country on Saturday announced a lockdown of its capital region after an outbreak of a more contagious coronavirus variant, first identified in Britain.

Among the measures introduced on Jan 23., non-essential stores in and around Oslo are currently closed for the first time in the pandemic.

Norway is seeing declining levels of infections by the coronavirus however, said Solberg. The county’s reproduction rate, which indicates how many people on average an infected person transmits the virus to, stands at 0.6, she added.

Norway has one of the lowest rates of new infections in Europe per 100,000 inhabitants, according to the European Centre for Disease Prevention and Control.

While sailors on merchant ships are still permitted to travel, the Norwegian Shipowners’ Association (NSA) questioned the prime minister’s plan.

“This will be very challenging,” NSA Chief Executive Harald Solberg said.

“We need rapid decisions on, and improvements to, compensations for all those who will now face the consequences,” he said.

(Reporting by Gwladys Fouche and Terje Solsvik; Editing by Aurora Ellis)