Addressing world news industry leaders in Sweden on Tuesday, the chess grandmaster accused the agency's editor-in-chief, Svetlana Mironyuk, also present at the forum, of engaging in propaganda on the Kremlin's orders.
"Such accusations are absolutely groundless," the agency said in an official statement, while demanding a public apology from Kasparov.
Kasparov also reiterated his view at the World Newspaper Congress in Gothenburg that Vladimir Putin, Russia's former president and current prime minister, has crushed press freedom in Russia, and urged media executives to challenge the Kremlin on free speech issues.
Responding to Kasparov's comments at the congress, Yevgeny Abov, representing Russia's official newspaper Rossiyskaya Gazeta, said RIA Novosti provides "completely free" coverage.
The Other Russia, an umbrella group of opposition parties that includes Kasparov's United Civil Front, recounted the exchange on its website, saying Kasparov then asked if RIA Novosti would allow him to hold a press-conference, to which Abov replied in the affirmative.
RIA Novosti said in its statement that it follows international news standards and seeks to provide unbiased coverage, giving a voice to opposition leaders in its stories and translating critical foreign newspaper articles.
The agency provided statistics to back up its statement, saying it has published some 300 news stories related to Kasparov and other opposition figures, and hosted over 50 news conferences and other events involving fellow The Other Russia members.
The agency also said Kasparov had never requested a news conference at RIA Novosti.
A website run by RIA Novosti, www.inosmi.ru, has published 43 articles on Russia by Kasparov, the statement said.
The chess grandmaster pulled out of the Russian presidential race last December, saying the authorities had made it impossible for him to run.
The new President Dmitry Medvedev, Putin's ally and protege, has signaled his intention to liberalize media in the country.
