The top diplomats of South Korea and Russia barely discussed the controversial issue of deploying an advanced U.S. missile defense system on Korean soil during their talks earlier this week, a Seoul official said.

The senior official told South Korean reporters during a luncheon in St. Petersburg on Tuesday that the topic of the Terminal High Altitude Area Defense system was raised in the meeting between South Korean Foreign Minister Yun Byung-se and his Russian counterpart, Sergey Lavrov, but only in passing.

"(The Russian side) mentioned a confrontational structure in Asia but barely talked about it," the official said, speaking on the condition of anonymity. "This showed (Moscow's) will to focus more on bilateral relations and the North Korean nuclear issue."

Russia and China have strongly opposed the possible deployment of a THAAD battery to South Korea, claiming it would undermine the strategic balance in the region. Seoul and Washington insist the missile defense system, if placed in the South, would be purely defensive in the face of North Korea's evolving nuclear and missile threats.

The official highlighted the effort Moscow made to ensure the success of Monday's talks.

"Because Russia is placing more importance on Asia, it has begun to give more attention to South Korea, and the expression it's begun to use recently is that South Korea is a key partner in Russia's foreign policy," he said.

Analysts say Russia is increasingly looking east for new business opportunities amid an economic crisis caused by low global oil prices and international sanctions against the country.

As both China and Japan are seen as rivals in terms of geopolitics or territory, South Korea could be an optimum partner for Russia with all the necessary technology and resources but almost no source of tension between the two sides.

In a speech at a conference of the Korea-Russia Dialogue forum Tuesday, Yun said Lavrov agreed with him on the large potential for bilateral cooperation in developing Russia's Far East region.

He also noted the similarity between Russia's new "Look East"

policy, which centers on developing the Far East, and South Korea's Eurasia Initiative, which aims to draw countries in Asia and Europe closer by increasing rail, infrastructure and IT links.

Yun was the first South Korean foreign minister to visit Russia in five years. His three-day trip included talks with Lavrov in Moscow on Monday and various events in St. Petersburg on Tuesday.

The visit was seen as part of Seoul's efforts to strengthen the international sanctions regime against Pyongyang following its fourth nuclear test and its long-range rocket launch early this year.

"In the past, Russia was very careful about mentioning North Korea," the official pointed out during the luncheon. "They disliked criticizing the North even more and never used the word 'condemn' (on North Korea)."

However, in a press conference following Monday's talks, the two ministers said they agreed not to recognize North Korea as a nuclear weapons state and to strengthen their cooperation for the North's denuclearization.

"Russia has changed a lot in that it's showing its strength regarding the North Korea issue," the official said.

Moscow is a key stakeholder in efforts to dismantle the North's nuclear weapons program. It is one of five veto-wielding permanent members of the U.N. Security Council, which adopted a resolution in March imposing the toughest yet sanctions on Pyongyang, and a member of the now-stalled six-party talks on the North's nuclear program.

Before leaving, Yun visited a cemetery where he laid a wreath in front of a monument honoring Lee Beom-jin, Korea's diplomatic representative to the Russian Empire in the early 1900s. Lee fought for Korea's sovereignty in the face of Japanese aggression but killed himself at his St. Petersburg home in 1911 in protest of Japan's annexation of Korea.

The foreign minister also toured a Hyundai Motor plant located northwest of the city, the only foreign-owned car plant in Russia that handles the entire production process from parts manufacturing to assembly.

The South Korean automaker has expanded its presence in the Russian car market since it began local production in 2011. Last year, its share reached 20 percent of new cars.

The 200 hectare plant produces some 200,000 cars annually for sale in and outside the country and employs more than 7,000 locals.

From Russia, Yun headed to Bulgaria, where he held talks with his Bulgarian counterpart Daniel Mitov on Wednesday. (Yonhap)