Britain's ambassador to Zimbabwe intends seeking legal advice after the main government daily published a "completely fabricated" story about embassy aides assaulting a freelance journalist.

"If any one read @herald this morning, story from Kariba is complete fabrication. Will be lodging complaint to editor + seeking legal advice," Catriona Lang tweeted.

In the story, freelancer Edmore Mbonda said he had heard Lang was in Kariba and wanted to ask her questions. He went to a hotel in Kariba, but embassy security ordered him to leave. He claimed one of them kicked him on the leg "causing him to fall".

A quick online search did not turn up any bylines for Mbonda.

The Herald quoted a British embassy spokesperson as saying the story was "ridiculous".

A protest movement with the hashtag #ThisFlag, founded by pastor Evan Mawarire, is gaining in popularity in Zimbabwe. Mawarire started it when he filmed himself with the country’s flag around his neck, expressing his frustrations about the country’s government.

A major grouping of war veterans on Wednesday called President Robert Mugabe "dictatorial" and said they would no longer back him.

Until now, the war veterans have been Mugabe's most loyal backers. That role could be taken over by ruling party youths, analysts said.

Mugabe's government said Mawarire was funded by the West and that it was using him to bring about regime change in Zimbabwe.