May 17 (Bloomberg) -- Estonia, the former Soviet republic on the Baltic sea that's locked in a dispute with Russia, appealed to NATO to help defend it against a ``cyber attack'' linked to Russian Web sites.

The ``cyber warfare'' that began on April 27 jammed and disabled the Web sites of the president's office, parliament, ministries, major newspapers and banks, said Rica Semjonova, a spokeswoman for the government agency handling the attacks.

``No state has been attacked over the Internet as massively as Estonia,'' Defense Ministry spokesman Madis Mikko said in a telephone interview today in Tallinn. A spokesman for President Vladimir Putin denied any Russian involvement.

Estonia, a country of 1.4 million, has been a member of the North Atlantic Treaty Organization and the European Union since 2004. It is one of the most advanced users of the Internet in the world and has pioneered a system of electronic government, making it particularly vulnerable to Web-based attacks.

NATO sent an expert to Tallinn and a new cyber center has been set up that is in contact with specialists in NATO countries ``all the time,'' said Mikko.

The Web sites affected have been jammed by tens of thousands of visits from all over the world. Estonian officials say that in the early phase of the onslaught, many Internet addresses from which visits came were traced to Russia, including the Kremlin.

Estonian Defense Minister Jaak Aviksoo asked for NATO to set out a clear policy for cyber defense at a meeting in Brussels on May 14. Foreign Minister Urmas Paet also requested the EU raise the issue ``at the highest level'' ahead of today's EU-Russia summit, the Estonian foreign ministry said.

Legislation Impotent

``If a power station is attacked and destroyed by a rocket, it is deemed a military attack, but if it is attacked over the Internet and the same result is achieved, international legislation cannot deal with it,'' said Mikko.

The dispute with Russia began on April 27, when a memorial to Soviet soldiers who died in World War II was moved from the center of Tallinn, Estonia's capital. Ethnic Russians staged protests in which one person was killed and 153 injured. The decision was followed by angry protests by Kremlin youth activists outside the Estonian embassy in Moscow.

Aivar Pau, online editor of Eesti Paeevaleht, the second- biggest daily in Estonia, whose Web site was targeted on May 15, said he was sure Russia stood behind the attacks.

``I am convinced that these attacks are directly connected to the removal of the Bronze Soldier and behind these are the same forces in Russia who tried to block the Estonian embassy and incite violence in Estonia,'' he said.

`Out of the Question'

Estonian officials have stepped back from directly accusing Russia over the cyber attacks. The Kremlin denies any involvement.

``It is out of the question that any Russian bodies could be involved in such attacks,'' said President Vladimir Putin's spokesman, Dmitry Peskov, by telephone today.

Estonia has responded by closing the sites under attack to foreign Internet addresses in an effort to keep them accessible for domestic users, said Semjonova.

``This is serious because much of the business of the country is done electronically,'' NATO spokesman James Appathurai said today by telephone from Brussels. ``Because it's serious for Estonia, it's serious for NATO.''

To contact the reporters on this story: Henry Meyer in Moscow at Hmeyer4@bloomberg.netOtt Ummelas in Tallinn at oummelas@bloomberg.net

Last Updated: May 17, 2007 09:40 EDT