Kiev (AFP) - The Ukrainian presidency said its website had been attacked by Russia in apparent retaliation for Kiev's decision to block prominent Moscow-based social networks.
"We have been witnessing the Russian response to the president's decree about closing access to Russian social networks," President Petro Poroshenko's deputy administration chief Dmytro Shymkiv said in a statement posted late Tuesday on Facebook.
"The president's website has sustained an organised attack."
Shymkiv added that IT specialists had the situation under control and that the website was no longer under threat. It was accessible on Wednesday in Kiev.
Kremlin spokesman Dmitry Peskov called Kiev's accusations unfounded.
"The absence of anything concrete (in Ukraine's claim) once again confirms the absolute baselessness of such accusations," Peskov told reporters.
IT specialists and Western governments are rarely able to pin a hacking attack directly on the Kremlin but often accuse groups or individuals close to the Russian government of being responsible for them.
Ukraine on Tuesday blocked Russia's most popular social media networks and an internet search engine in response to the Kremlin's backing of a three-year separatist war in the east and annexation of Crimea in March 2014.
The decision sparked an outcry from Ukrainian internet users and freedom of speech advocates.
"In a single move Poroshenko dealt a terrible blow to freedom of expression in Ukraine," Human Rights Watch researcher Tanya Cooper said.
"It's an inexcusable violation of Ukrainians' right to information of their choice," she said in a statement Wednesday.
It also sowed confusion among Ukraine's internet providers about how precisely such a ban would work.
The Internet Association of Ukraine sent a letter to Poroshenko and top government agencies asking how it should proceed since the former Soviet republic had no laws setting guidelines for blocking traffic to specific websites.
Several of the banned Russian social media sites published instructions to their users explaining how they could circumnavigate the ban by using open-access internet technologies.