The cyberattack follows attacks on other major media websites which include the New York Times and Wall Street Journal.
The Czech Republic's major news websites have become the latest victims of cyberattacks, as part of an onslaught carried out by hackers on media websites throughout the world.
Reuters said executives from three of the Central European state's most widely read online titles - ihned.cz, idnes.cz and novinky.cz -have confirmed the slowing or crashing of their web pages.
Hackers used distributed denial-of-service attack (DDoS attack), to overwhelm the system and make network resources unavailable to its intended users.
Lucie Tvaruzkova, the head of www.ihned.cz told Reuters, "We are receiving great numbers of requests at our servers, which is a typical way to attack."