SEOUL - Flight data on the arrival board of Vladivostok International Airport in Russia showed that North Korea's national airline Air Koryo is flying extra flights on Monday (July 30) to the Russian port city.

Five flights from Air Koryo are scheduled to fly from Pyongyang to Vladivostok on Monday, reported NK News, a website that monitors North Korea.

Of the five flights, three are said to be using the type of aircraft that North Korean leader Kim Jong Un uses to transport his armoured limousine when he travels overseas, said NK News. They are the Ilyushin-76 cargo plane. The other two are passenger jets Il-62 and Tupolev-154.

"Today (Air Koryo is) flying extra flights apart from standard passenger ones," NK News reported on Monday, quoting a spokesman from the airport of Vladivostok, a city near the borders with North Korea and China.

The spokesman added that two of the scheduled flights are for carrying passengers and the rest are for cargo, NK News added.

Another peculiarity is the use of the Ilyushin-76 plane, which is reportedly rare for cargo flights between Pyongyang and Vladivostok. Data between 2010 and 2018 from the NK Pro Aviation Tracker showed that this particular type of aircraft was not used for flights during those years, NK News noted.

The news website said it was not clear what was to be transported between the North Korean capital and the Russian city on Monday.

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NK News added that Air Koryo's round-trip flights between the two cities are usually scheduled twice a week - one flight each on Monday and Friday. However, on some of those two days in recent weeks, extra flights for passengers have been added, NK News noted.

The report said that the extra flight codes were only noticed incidentally by NK News recently as they were not part of Air Koryo's published summer timetable. This suggests that these additional flights were deployed to help cope with extra passenger demand.

According to NK News, some of these flights have recently been operated with Air Koryo IL-62M passenger plane, which is the same type that Mr Kim uses as his state aircraft.

As a result, South Korea's Yonhap news agency - as well as other media organisations - had reported that Mr Kim's plane was spotted in Vladivostok in July. The Russian airport had denied that.

Russian ambassador to North Korea, Mr Alexander Matsegora, had told Russia's RIA news agency on July 18 that a summit between Mr Kim and Russian President Vladimir Putin was "on the agenda".

Mr Kim did meet Russian Foreign Minister Sergei Lavrov in May.

A summit between Mr Kim and Mr Putin is widely expected, but a date remains unclear.