"In the morning, distributed denial-of-service (DDoS) attacks on the конституция2020.рф site were recorded. Presumably from the UK and Singapore," the commission said.
The website конституция2020.рф contains information on amendments to the constitution and voting procedures.
Earlier, on the first day of the amendment vote, a DDos attack on the Russian Central Election Commission website was reported.
Russians started voting on the proposed changes to the constitution on Wednesday, and polling stations will remain open until 1 July. The voting date had initially been set for 22 April but was postponed due to the outbreak of the coronavirus disease.