Ukraine's security service said foreign "saboteurs" had knocked out state television transmissions for several hours, suggesting Moscow had backed the action as part of a campaign fomenting rebellion in the east.
Viktoria Syumar, deputy head of security service, or SBU, said separatists had set fire to underground cables carrying power and signals to the broadcaster and several radio stations on the morning the country, and Russia, marks World War II Victory Day.
"The logic of the Russian special services to this very day is based on the teachings of Lenin on the priority of 'post, telephone and telegraph'," she said in reference to the Bolshevik leader's seizure of power in 1917.
"According to preliminary details, they set fire to cables in the tunnel, which could be accessed from the street and introduced flammable material. Only professionals know of such underground canals. This is classic sabotage."
The Kiev mayor's office had earlier said the fire had been due to a short circuit.
State television returned to the air broadcasting a talk show about Victory Day celebrations which have become a source of tension with Russia.
Kiev accuses its Soviet-era masters in Moscow of backing armed rebellion in the east of the country.