Ukraine has taken a further step in cutting the cord with Russia: President Petro Poroshenko has put in place new sanctions on Russian social media and web services. Popular networks like VKontakte and Odnoklassniki (classmates), the email service Mail.ru and the search engine Yandex will be blocked for three years, officials announced on Tuesday. Since Moscow's annexation of Crimea in 2014, Ukraine has banned Russian television broadcasters, and is now expanding the list of sanctions to include major Russian websites.

Just hours after the Tuesday announcement, Kyiv representatives accused Russia of launching a cyber-attack against the website of Ukraine's President Petro Poroshenko.

The attackers were using resources of Yandex and Vkontakte to create "artificial traffic in order to overload and bring down the servers," deputy head of the presidential administration, Dmytro Shymkiv, said in a statement posted on Facebook.

"The situation is under control thanks to our IT specialists and there is no threat to the work of the website," he said.

Moscow did not immediately comment on these claims.

Ukrainians prefer Vkontakte to Facebook

When the internet took hold in the 1990s in the former Soviet republic, the Russian language dominated websites and forums. Due to their familiarity with the Russian language, most Ukrainians used Russian email services and social networks, which were generally of a superior quality.

The annexation of Crimea and the war in eastern Ukraine brought about a shift in attitude. Studies show that more and more, Ukrainians have been turning to domestic or Western services, like Google, which is now number one search engine in Ukraine. However, Vkontakte, Russia's leading social network, is still more popular among Ukrainians than Facebook.

A blow to 'Russian propaganda'

In the past three years, there have been increasing calls to stop using web services provided by the "aggressor state," as Russia is often referred to in Ukraine. But not much has been done about it. The Security Service of Ukraine (SBU) advised Ukrainians to stop using Russian social networks. Kyiv warned Ukrainian internet users that Russia's state security organization, FSB, had access to their private data, and Ukrainian civil servants had to stop using Russian web services for work.

Zoryan Shkiryak, an advisor to Ukrainian Minister of Internal Affairs Arsen Borysovych Avakov, campaigned for a general ban in February and is pleased about the the latest move. "I see this as our mutual victory in the information war against the aggressor in the Kremlin," he wrote on Facebook.

However, the president's decree goes beyond social networks. Many now warn against the business activities of the newly-blocked Russian search engine Yandex, which has been expanding its range of services to include maps and news in Ukraine in recent years, despite the political crisis between Moscow and Kyiv.

An attack on press freedom?

It is still unclear how the sanctions will be enforced. Millions of Ukrainians are anxious about what will happen to their data and their contacts on Russian networks. Experts say it will be hard to implement the sanctions - legally and technically.

"Ukraine is not a country that will remain silent if press freedom is attacked," Oksana Romaniuk, head of the Kyiv-based Institute of Mass Information (IMI), told DW. She, too, doubts the sanctions will be fully implemented.

Other critics view President Poroshenko's decision as counterproductive, since Ukrainian intelligence agencies have also benefited from information on Russian networks - to collect data on the separatists in eastern Ukraine, for example.