An increased troop presence in Zimbabwe's capital has triggered speculation about a potential military coup, a day after a warning from the top army general to President Robert Mugabe.
Eyewitnesses also said on Tuesday army tanks were seen about 20 kilometres west of the capital, Harare.
On Monday, top army general Constantino Chiwenga warned Mugabe that the military will "step in" if the president continues to expel former liberation fighters from the ruling Zanu-PF party who are supporters of the sacked vice president.
"We are surprised to see these army tanks along the Chinhoyi-Harare highway. Especially now when the army chief has threatened to step in, I think that something is going to happen soon," witness Clement Gomo, who was driving towards Chinhoyi, told German news agency DPA by phone.
Harare resident Vivian Chinhengo said soldiers were deployed in Harare's central business district.
"I seen some soldiers at almost every intersection in the city today," she said. "It is very unusual considering that we normally see a few soldiers in uniforms during their pay days."
An official said, however, that Mugabe was going about his business as usual. A DPA reporter saw the president's official vehicle and motorcade parked at his office in the afternoon.
Mugabe has threatened to fire more than 100 officials linked to Emmerson Mnangagwa, the vice president he sacked last week and who enjoys the support of the influential War Veterans' Association.
"The current purging, which is clearly targeting members of the party with a liberation background, must stop," said Chiwenga, flanked by senior army personnel.
Mnangagwa had long been tipped as Mugabe's most likely successor but has in recent months increasingly come into conflict with first lady Grace Mugabe, who is vying to replace the 93-year-old president.