U.S. President Donald Trump showed a screenshot of Reuters video taken in the Democratic Republic of Congo as part of what he falsely presented on Wednesday as evidence of mass killings of white South Africans.

"These are all white farmers that are being buried," said Trump, holding up a print-out of an article accompanied by the picture during a contentious Oval Office meeting with South African President Cyril Ramaphosa.

In fact, the video, published by Reuters on February 3 and subsequently verified by the news agency's fact-check team, showed humanitarian workers lifting body bags in the Congolese city of Goma. The image was pulled from Reuters footage shot following deadly battles with Rwanda-backed M23 rebels.

The blog post showed to Ramaphosa by Trump during the White House meeting was published by American Thinker, a conservative online magazine, about conflict and racial tensions in South Africa and Congo.

The post did not caption the image but identified it as a "YouTube screen grab" with a link to a video news report about Congo on YouTube, which credited Reuters.

The White House did not respond to a request for comment. Andrea Widburg, managing editor at American Thinker and the author of the post in question, wrote in reply to a Reuters query that Trump had "misidentified the image."

She added, however, that the post, which referred to what it called Ramaphosa's "dysfunctional, race-obsessed Marxist government", had "pointed out the increasing pressure placed on white South Africans."

The footage from which the picture was taken shows a mass burial following an M23 assault on Goma, filmed by Reuters video journalist Djaffar Al Katanty.

"That day, it was extremely difficult for journalists to get in ... I had to negotiate directly with M23 and coordinate with the ICRC to be allowed to film," Al Katanty said. "Only Reuters has video."

Al Katanty said seeing Trump holding the article with the screengrab of his video came as a shock.

"In view of all the world, President Trump used my image, used what I filmed in DRC to try to convince President Ramaphosa that in his country, white people are being killed by Black people," Al Katanty said.

Ramaphosa visited Washington this week to try to mend ties with the United States after persistent criticism from Trump in recent months over South Africa's land laws, foreign policy, and alleged bad treatment of its white minority, which South Africa denies.

Trump interrupted the televised meeting with Ramaphosa to play a video, which he said showed evidence of genocide of white farmers in South Africa. This conspiracy theory, which has circulated in far-right chat rooms for years, is based on false claims.

Trump then proceeded to flip through printed copies of articles that he said detailed murders of white South Africans, saying "death, death, death, horrible death".