Poland will introduce a mandatory 10-day quarantine for travellers from outside the Schengen Area, from midnight.
While the country's daily COVID-19 cases have decreased sharply since the peak of the third wave in spring, authorities are worried about the presence of strains such as the more contagious Delta variant in the country.
"We see that these new mutations have arrived in our country," Deputy Health Minister Waldemar Kraska told a news conference.
"Due to the fact that these new variants spread faster... we are taking preventative action."
The quarantine regulations will not apply to people who are fully vaccinated, or children under 12 travelling with vaccinated adults, he added.
It will be possible to be released from quarantine if a test taken after seven days is negative, he said.
On Tuesday, Poland announced it was tightening quarantine rules for travellers from Britain due to concerns about the Delta variant, which was first identified in India.
Poland, a country of around 38 million people, has reported 2,879,192 cases of the coronavirus and 74,893 deaths.
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