Estonian Prime Minister Kaja Kallas called for preparations for rolling blackouts if Russia excludes the Baltic states from the common energy system and announced a surprise defense preparedness exercise, Reuters reported.

"We must also be prepared for Russia might disconnect Estonia, Latvia, and Lithuania from their electricity grid", she said in a televised address on Thursday evening, according to the government website.

"It would be wise to be prepared for possible power outages – that includes public authorities, companies, and every individual", she added, describing any disruptions as "temporary".

Nearly 3,000 reservists were called in Thursday for Estonia's annual weeklong defense drill, but the prime minister said there was no immediate military threat to the country.

Lithuania, Latvia and Estonia remain dependent on a stable energy supply from Russia.

The 1.6 billion-euro EU-funded project aims to disconnect the Baltic states from their common power grid with Russia and Belarus in 2025 in favor of a decentralized grid in continental Europe.

Europe's ENTSO-E power grid will connect to the Baltic states' networks within 24 hours if the countries are cut off by Russia, helping to avoid blackouts, Lithuanian power grid operator Litgrid said in July. "If Russia disconnects us, even today, we would be ready. Our analysis shows that power supply would not be rationed, no serious disruptions expected," Litgrid Chief Executive said.