July 11 (UPI) -- A top North Korean official visited Moscow on Tuesday, raising the possibility of a future summit between Russian President Vladimir Putin and Kim Jong Un.
Ri Su Yong, vice chairman of the ruling Workers' Party's Central Committee, was escorted by North Korean Embassy staff upon landing at the airport, according to Nippon TV.
Ri was likely flying in from Cuba, where he had met with Miguel Díaz-Canel Bermúdez, the current president of the country.
The two politicians met on Saturday and Ri left the country on Monday, according to South Korean news service News 1.
According to Nippon TV, it is likely Ri was visiting Moscow to discuss a Kim visit to Russia.
Putin has invited the North Korean leader to the Eastern Economic Forum in Vladivostok, but Kim has yet to reply.
The two sides did agree to eventually hold a summit in 2018.
Speculation has been building in Seoul that a North Korean working group was in Vladivostok to make arrangements after recent flight data showed North Korean Air Force One, also known as Chammae-1, flew to Vladivostok and back.
South Korea is also trying to engage the North economically, and as part of its efforts will be sending Song Young-gil, the head of an inter-Korea economic cooperation committee to the North Korean city of Rason, Yonhap reported Wednesday.
The city was a hub for a project involving the transport of Russian coal to South Korea through the Rajin-Hasan Railway that runs through North Korea.
The project was suspended, owing to North Korea nuclear tensions more than three years ago, although it had managed to sidestep South Korean sanctions through former President Park Geun-hye's Eurasia Initiative.
Coal was delivered using the route in 2014 and 2015 but was subsequently suspended.