SEOUL, Sept. 10 (Xinhua) -- South Korean Prime Minister Lee Nak-yon left Monday for Russia's Vladivostok to attend the Eastern Economic Forum, an annual international economic forum hosted by Russian President Vladimir Putin.

Lee will stay for three days in the Russian city, delivering a keynote speech at the forum on Wednesday.

During the speech, Lee planned to explain the New Northern Policy, which was advocated by South Korean President Moon Jae-in to deepen relations with Russia, Mongolia and other northern countries.

The Eastern Economic Forum has been held annually since 2015. This year's forum was expected to be attended by about 6,000 people. The South Korean president attended last year's forum.