A 20-year-old Estonian student has been fined for participating in a cyberattack that paralyzed Estonian Web sites and soured the country's relationship with Russia, a government official said Thursday.

Dmitri Galushkevich used his home PC to launched a denial-of-service attack that knocked down the Web site for the political party of Estonia's prime minister for several days, said Gerrit Maesalu, spokesman for the Northeast District Prosecutor's Office in Tallinn, Estonia's capital. Galushkevich must pay 17,500 kroons ($1,642).

Galushkevich is the only person who has been convicted since the cyberattack in April and May 2007 crippled the Web sites of banks, schools, and government agencies.

The attacks occurred after the Estonian government decided to relocate a Soviet-era World War II memorial of a bronze soldier. Ethnic Russians in Estonia rioted in the streets, and cyberattacks ensued. Russia denied involvement.

"He [Galushkevich] wanted to show that he was against the removal of this bronze statue," Maesalu. "At the moment, we don't have any other suspects."

But police are still trying to find others who may have been involved in the attacks, although the investigation is complicated since the attackers are likely outside Estonia, Maesalu said.

As the attacks were continuing, Estonian Defense Minister Jaak Aaviksoo called for stronger defenses in Europe against computer hackers.