In this May 26, 2018, file photo, people watch a TV screen showing file footage of U.S. President Donald Trump, right, and North Korean leader Kim Jong-un during a news program at the Seoul Railway Station in Seoul, South Korea. Kim is on a rare trip abroad as he leaves the all-encompassing bubble of his locked-down stronghold of Pyongyang and steps off a jet onto Singaporean soil for his planned sit-down with Trump on Tuesday, June 12, 2018. / AP

By Park Si-soo

A Chinese Boeing 747-4J6 private jet is flying to Singapore after taking off from an airport in Pyongyang, North Korea's capital, South Korea's Yonhap News Agency reported on Sunday, citing a flight route-tracking website (https://www.flightradar24.com/CCA061/11ac2ef5).

The takeoff of an Air China plane was detected at 8:30 a.m., according to Flightradar24.

One hour later, Kim's private jet also took off from Pyongyang for Singapore.

The North Korean leader and his entourage are on one or the other of the flights. The two planes are travelling in Chinese airspace, apparently for security reasons.

While the real-time location of the Chinese jet can be traced with the website, Kim's private jet "Chammae 1" is untraceable because its code name is confidential.

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Kim is expected to arrive in Singapore on Sunday evening.

U.S. President Donald Trump has left for Singapore from Canada after attending a two-day Group of Seven (G7) meeting that ended on Saturday. Trump is expected to land at a military air base in Singapore on Sunday night.

Kim and Trump will have their historic summit on Tuesday to discuss the North's denuclearization.

The Singapore government said its Prime Minister Lee Hsien Loong would meet Kim and Trump separately on Sunday and Monday.