The officials were reportedly executed after the February talks between North Korea and the US came to an end without any deal being made.
Pyongyang had accused the four officials of selling information to Washington before the Hanoi summit, according to a Japanese news agency.
The executions, which included a diplomat from North Korea’s embassy in Hanoi, have not been verified.
Asia Press claimed its reporter spoke to a trade official who was told the rumour about the executions.
It is claimed that the executions were watched by members of the ruling Workers’ Party of Korea and Korean People’s Army.
The Hanoi summit had the aim of achieving denuclearisation on the Korean Peninsula and North Korea was hoping to have its sanctions lifted.
When the talks failed, Washington insisted that dialogue with North Korea would continue and that the collapse was not a major disappointment.
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Following the summit, President Trump said: “Kim is a person I’ve gotten to know very well, and respect and hopefully, and I really believe over a period of time, a lot of tremendous things will happen.
“I think North Korea has a tremendous potential.”
Kim arrived in Russia on Wednesday, April 24 to discuss bilateral ties with President Vladimir Putin.
North Korea’s leader has said he was hoping for a “successful and useful” visit where he hopes to discuss the situation in the Korean Peninsula.