The websites of Ukrainian President Viktor Yanukovich and the interior ministry have been put out of action by angry internet users.
Government websites have been bombarded with automated requests as a protest against at the shutting down of a popular file-sharing website.
Ukrainian police closed the site, which is used by millions of Ukrainians to obtain movies, music and software for free. The authorities accuse it of copyright piracy.
Police say they had received numerous complaints against the site from software companies such as Adobe and had been investigating it since last July 2011.