Ukraine will block access to the country's most popular social networking sites and other Russian-based web businesses under new sanctions against Russia for its annexation of Crimea and war in east Ukraine.

Access to Yandex, a Russian equivalent of google that provides search engines, maps, and other popular tools, and social media sites Vkontakte and Odnoklassniki, will be banned under a decree signed by Petro Poroshenko, the president of Ukraine, on Tuesday.

The decree bans Ukrainian web hosts from linking to the Russian websites from May 15.

The decision was described in a decree posted on the presidential website as part of economic sanctions against Russia, which annexed Crimea from Ukraine in 2014 and has sent weapons, equipment, and troops to support a fuel the separatist side in a war in eastern Ukraine.

However, some Ukrainian officials have also described it as a national security measure.

"The servers of these Russian social networks ... store the personal data of Ukrainian users and information on their movements, contacts, communications," Volodymyr Ariev, an MP from President Petro Poroshenko's political faction, said on Facebook.

Other websites blocked under the order include those of the cyber security firms Kaspersky Lab and DrWeb.

The decrees also imposes asset freezes and broadcast bans on Russian television channels TV Tsentr, RBK, VGTRK, NTV-Plus, Zvezda, TNT, REN and ORT.