Reuters journalists in multiple locations were unable to access the All-Russia State Television and Radio Broadcasting Company (VGTRK) website or the Smotrim live-streaming platform for periods during the speech.
A message on the VGTRK website said that "technical works were being carried out" while the Smotrim website was not loading.
Shortly before the speech started, state TV channels had broadcast a segment on the technical preparations that go into broadcasting the speech, saying the live stream would be carried across all major Russian TV channels.
The state-run RIA Novosti news agency said the outage was the result of a distributed denial of service (DDoS) attack.
Reuters was unable to independently verify the reason for the outages.
(Reporting by Reuters)