Chinese officials are denying the North Korean presence in their capital.
North Korean Foreign Minister Ri Yong Ho, who made headlines in 2017 for suggesting Pyongyang could detonate a hydrogen bomb over the Pacific Ocean, was visiting Swedish Prime Minister Stefan Löfven's Rosenbad office on Friday, South Korean news service News 1 reported.
On Thursday, Ri is believed to have met with Swedish Foreign Minister Margot Valstrom, and has extended his stay to four days, according to the report and Swedish national public TV broadcaster SVT.
Choe Gang Il, the North Korean deputy chief for North American affairs, was seen in Beijing in a trip where he accompanied Ri, until the foreign minister left for Europe, Yonhap reported Friday.
The South Korean news agency reported Choe stayed behind in China and Choe was not included in the list of passengers for Scandinavian Airlines flight SK9511, which Ri boarded to begin his diplomatic visit to Sweden.
Ri was also not seen in a North Korean embassy vehicle that was taking Choe out of the airport's third terminal.
Beijing foreign ministry spokesman Lu Kang said Friday that he "does not know of the situation," regarding Choe.
China and Sweden could be potential locations for the summit.
Ahead of the planned meeting, Trump is defying his critics who are slamming him for his lack of caution and willingness to meet Kim.
"This is the biggest thing that's happened in 40 years," Trump said, at a private fundraiser event on Wednesday, according to The Washington Post.
He also said he disagrees with those who say he "conceded" to Kim.
"And I tell this Korea story because it was, it was somewhat of a miracle. It's actually far ahead of schedule. And you know, you hear that we're making a major concession by agreeing to the meeting, you know, it's the craziest thing. But go back a couple of weeks earlier and listen to what -- they were petrified."