Russian users of Telegram and WhatsApp had trouble accessing the messaging apps on Wednesday due to disruption the state communications monitoring service said was caused by a distributed denial-of-service (DDoS) attack.
The service said the attack had been repelled and that the messaging networks were working normally again. Russian media said other sites, including Wikipedia, Skype and the social media platform Discord had also been affected, Reuters reported.
"The disruption is related to a DDoS attack on Russian telecom operators," the service said in a statement, without saying who might have been responsible.
Wednesday's disruption to the messaging apps, which are widely popular in Russia, came weeks after Russian internet monitoring services reported a mass outage on the availability of video hosting site YouTube as Russian authorities step up criticism of the platform.
Hundreds of Russian users of Signal reported glitches with the secure messenger app earlier this month.
Russia began to block access to Telegram in 2018. The action interrupted many third-party services, but had little effect on the availability of Telegram there.
WhatsApp's parent company Meta Platforms Inc was branded an "extremist" organisation by Moscow in 2022 and other Meta services - Facebook and Instagram - are now banned in Russia, but can still be accessed using virtual private networks (VPNs).