The Associated Press saw three tanks with several soldiers in a convoy on a road heading toward an army barracks just outside the capital, Harare.
While it is routine for tanks to move along that route, the timing heightened unease in this southern African country that for the first time is seeing an open rift between the military and 93-year-old President Robert Mugabe. The military has been a key pillar of Mugabe's power since independence from white minority rule in 1980.
Mnangagwa, who enjoyed the backing of the military and was once seen as a potential successor to Mugabe, fled the country and said he and his family had been threatened. Over 100 senior officials allegedly supporting him have been listed for disciplinary measures by a faction associated with Mugabe's wife, Grace Mugabe.
The first lady, whose political profile has risen in the past few years, now appears positioned to replace Mnangagwa, leading many in Zimbabwe to suspect that she could succeed her husband as president.
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"We must remind those behind the current treacherous shenanigans that when it comes to matters of protecting our revolution, the military will not hesitate to step in," the army commander said.
Mugabe did not respond to the military statement, and government spokesman Simon Khaya Moyo said only the president could respond. The state-run broadcaster did not report on the statement.
The ruling party's youth league, aligned to the first lady, on Tuesday criticized the army commander's statement, saying youth were "ready to die for Mugabe."