BEIJING, An airplane presumed to be the private jet of North Korean leader Kim Jong-un was spotted in Vladivostok on Monday, raising speculation that preparations might be underway for him to travel to Russia in the near future.

According to Flightradar24, a flight tracking website, Kim's private jet, also known as Chammae-1, landed at an airport in Vladivostok earlier in the day and took off for Pyongyang about three hours later.

It has not been confirmed whether Kim was on board. Speculation still lingers that the plane could have been used for North Korean officials to visit Vladivostok and make preparations for their leader's possible trip to the city in time for a major economic forum there.

"There is no guarantee that Chairman Kim was on board just because the Chammae-1 moved," a source said. "It appears that North Korean officials have traveled there to make preparations for Kim's possible participation in the Eastern Economic Forum to be held in Vladivostok this September."

In May, Russian President Vladimir Putin invited Kim to the annual forum. Kim has not responded to the invitation yet.

This year's event is drawing special attention as it comes after North Korea, South Korea and the United States promised to work toward the complete denuclearization of the Korean Peninsula.

South Korean President Moon Jae-in was invited to take part in the forum. Russia has also asked Japanese Prime Minister Shinzo Abe and Chinese President Xi Jinping to attend.

Should all those leaders, including Kim, join the forum, it could provide a rare chance for five of the long-suspended six-party negotiation members to get together and discuss the North's nuclear issue on the sidelines.

Source: Yonhap News Agency