Donald Trump has struck an upbeat tone about North Korea despite a failed Hanoi summit in February (FILE)

U.S. President Donald Trump on Wednesday appeared to cast doubt on news reports of North Korean executions as part of a purge in the aftermath of a failed Hanoi summit and lamented that North Korean leader Kim Jong Un was blamed too quickly.

Asked about South Korean reports that North Korea had executed a top diplomat, Trump said, "I don't know if the reports are correct."

"They like to blame Kim Jong Un immediately," Trump said during an appearance with Irish Prime Minister Leo Varadkar.

Trump has famously sided with autocratic leaders, including saying last July he believed Russian President Vladimir Putin over U.S. intelligence findings that Russia had attempted to sway the 2016 presidential election.

In May, he said he agreed with the North Korean leader's criticism of former U.S. Vice President Joe Biden, a Democratic presidential candidate.

There have been conflicting reports about shakeups in the North Korean diplomatic team. South Korean newspaper Chosun Ilbo said last week that nuclear envoy Kim Hyok Chol was executed in March along with four foreign ministry officials after they were charged with spying for the United States.

Reuters was unable to independently confirm the account. Previously, some North Korean officials who were reported to have been executed or purged reappeared later with new titles.

CNN reported on Tuesday, however, that Kim Hyok Chol was alive and in state custody.

The South Korean newspaper said earlier that the former top nuclear negotiator, Kim Yong Chol, had been sent to a labour camp. He was then pictured on Monday in a state media photo accompanying Kim Jong Un to an art performance.

In his comments, Trump appeared to mistake the senior official who was reported to have been sent to hard labour for the negotiator who was reported to have been executed.

"They said he was killed but he wasn't. He was at the theatre the other night. So he wasn't killed. The other four people I know nothing about," Trump said.

The February summit in Vietnam's capital Hanoi, the second between Kim and Trump, failed to reach a deal because of conflicts over U.S. calls for Pyongyang's complete denuclearisation and North Korean demands for sanctions relief.

Diplomatic efforts have stalled since then, and North Korea conducted short-range missile tests last month.

But Trump struck an upbeat tone. "It's been going pretty well because there hasn't been testing of anything major," he said. "I think that Chairman Kim would like to make a deal and I'd like to make a deal with him, and I look forward to seeing him at the appropriate time."