Kim Chang Son, Kim's de facto chief of staff, flew to Singapore via Beijing on Monday night, the report said.
Japanese public broadcaster, NHK, reported Kim Chang Son's flight to Singapore on Tuesday.
At the same time, a team of US government officials, including the White House deputy chief of staff for operations Joe Hagin, left US Yokota Air Base in Japan for Singapore on Monday.
Earlier, after unexpected cancellation of his June meeting with North Korean leader ,Trump has talked about the readiness of US military in a war-mongering and threatening tone.
A summit between the two leader had been scheduled for June 12 in Singapore. Preparations had been underway since March, but Trump cancelled the meeting on Thursday, blaming Kim’s “tremendous anger and open hostility” for scuppering the talks.
Days earlier, North Korean Vice Minister Choe Son-hui had threatened to walk away from discussions if Washington continued to carry out its "unlawful and outrageous acts," including joint military exercises with South Korea.
