PRAGUE — The Czech Republic is further tightening entry rules in an effort to limit the growing spread of highly contagious variants of the coronavirus.

Travelers from high-risk countries have to present a negative PCR test on arrival that is not older than 72 hours and must go into quarantine for at least five days before another PCR test. They also have to fill in an online form before their trip and wear a respirator for the first 10 days of their visits.

High-risk countries include Britain, Ireland, Portugal, Spain, Slovakia, Slovenia, the Baltics states and most other countries outside the EU.

Those traveling from less risky countries are asked to present a fast antigen test on arrival.

The measure becomes effective on Friday.

The Czech Republic has already banned all tourist trips.