Moldova's pro-EU President Maia Sandu blames "criminal groups" working with "foreign forces" -- alluding to Moscow -- for a tight referendum on joining the EU.
Moldova's razor-thin vote in favour of joining complicates Sandu's quest for her small former Soviet republic to enter the bloc.
Although accession talks with the EU are expected to continue, Sandu faces a tough battle to defend her agenda, with a new electoral test looming in November.
Russia on Monday said the country's president must "prove" claims there had been foreign interference.