"We identified in the initial attacks IP numbers from the Russian governmental offices," Aaviksoo told The Associated Press by telephone. "There is not sufficient evidence of a governmental role, but it indicates a possibility."
He said more than 1 million computers worldwide have been used in recent weeks to attack Estonian Web sites since the removal of a disputed Soviet statue from downtown Tallinn.
When Estonia first pointed the finger at Russia on May 1, Kremlin spokesman Dmitry Peskov dismissed the accusations, saying the attackers must have used a fake Kremlin IP address to tarnish Russian authorities.
Aaviksoo said the attacks were massive and well-organized, targeting the government offices and a number of corporations including the six major banks in the Baltic country.
"They started after we discovered instructions on Russian Web sites telling when, why and what to attack," he added.
Aavikso said he had informed his colleagues in the European Union earlier this week about the situation and was confident the issue would be raised at an EU-Russia summit Friday in Samara.
"I'm sure this issue will be one of the talking points," the defense minister said. "I felt strong support from my partners."
The so-called denial-of-service attacks against Estonian Web sites started after the April 27 removal of the Bronze Soldier, which commemorates Red Army soldiers killed fighting the Nazis, but which many Estonians consider a bitter reminder of five decades of Soviet occupation.
The statue was removed from a downtown square and placed in a cemetery outside Tallinn, infuriating Moscow and Estonia's ethnic Russians, who said the move was an insult to the memory of the fallen soldiers.