Russia invited both President Park Geun-hye and Kim in December last year, but many have doubted that they would both turn up. It would be the first time a North Korean leader has ever appeared at an event with a group of other leaders.

North Korean leader Kim Jong-un has accepted Russia's invitation to 70th anniversary celebrations of its World War II victory in Moscow in May, the Itar-Tass news agency reported Wednesday.

Moscow invited the members of the British Commonwealth of Nations, Brazil, India, China, South Africa, the Shanghai Cooperation Organization, and the EU, as well as other countries in the anti-Hitler coalition and international and regional organizations.

Leaders of about 20 countries including Chinese President Xi Jinping have so far confirmed their attendance, Lavrov said. He did not say whether Park will attend or not.

A Cheong Wa Dae official said, "It's not clear yet whether Kim Jong-un will attend the event in Russia, and we aren't in a position to comment on his attendance. That's a matter between Pyongyang and Moscow. The question of Park's attendance at the Russian event is still under consideration."

"It's still about four months until the Russian celebrations, and no one knows how inter-Korean relations will develop by then," another Cheong Wa Dae official said. "It's too early to talk about an encounter or a summit between Park and Kim there."

In 2005, the leaders of China, France, Germany, Japan and the U.S. attended the event marking the 60th anniversary.

