WASHINGTON/SEOUL -- US President Donald Trump said Wednesday that North Korea has sent back the remains of 200 American soldiers who were killed in the 1950-53 Korean War.

The repatriation is part of an agreement Trump signed with North Korean leader Kim Jong-un at their historic summit in Singapore last week.

"Our great fallen heroes, the remains, in fact today already 200 have been sent back," Trump said at a rally in Duluth, Minnesota, noting that he had "great chemistry" and "got along really well" with Kim.

"They stopped shooting missiles over Japan. They stopped all nuclear testing. They stopped nuclear research. They stopped rocketry. They stopped everything that you'd want them to stop. And they blew up sites where they test and do the testing," he said, appearing to take credit for the actions North Korea has taken since it offered to discuss the dismantlement of its nuclear weapons program.

Trump has expressed frustration over criticism that he legitimized the communist regime and gave it concessions by meeting with the leader and agreeing to suspend military exercises between South Korea and the US In return, critics say, North Korea committed only to the vaguely worded "complete denuclearization" of the Korean Peninsula.

"Chairman Kim will turn that country into a great, successful country," said Trump. Referring to his term in office, he added, "Let me tell you this: a year and a half ago nobody thought that was possible."

To his supporters, he said, "Right now you are so safe, and such a great event took place, and all over Asia ... they're celebrating the great achievement that we made, because you were the ones that put me here."

CNN reported that it was unclear whether the remains had already been sent back or were planned to be sent back.

There was no official confirmation of the return from the relevant US authorities.

The South Korean government also said there was "nothing confirmed" yet regarding the issue. Responding to a media query, the Ministry of Foreign Affairs referred it to the US government.

"Our government hopes that the June 12 summit agreements between North Korea and the US, including the repatriation of US soldier remains, will be implemented swiftly to achieve the goals of completely denuclearizing the Korean Peninsula and establishing a peace regime," the ministry's spokesman Noh Kyu-duk said at a press briefing.

The remains of around 5,300 American service members are believed to be in North Korean territory, according to the Department of Defense POW/MIA Accounting Agency.

North Korea sent back the remains of 443 US soldiers between 1990 and 2007. (Yonhap)