Zimbabwean military officers read a statement on state TV in the early hours of Wednesday, saying they were not launching a coup but were "targeting criminals around" President Robert Mugabe.
Military vehicles blocked roads outside the Zimbabwean parliament Wednesday after army generals denied staging a coup.
The army has detained Finance Minister Ignatius Chombo, a source quoted by Reuters said.
The US embassy in Zimbabwe on Wednesday warned its citizens in the country to "shelter in place" due to "ongoing political uncertainty".
Gunfire erupted near President Robert Mugabe's private residence in Harare in the early hours of Wednesday
Several armoured vehicles were seen driving down main roads outside the Zimbabwean capital Tuesday evening, a day after the army warned it could intervene over a purge of ruling party officials.
Zimbabwe's ruling party on Tuesday accused the army chief of "treasonable conduct" after he challenged President Robert Mugabe over the sacking of the vice president.