“US citizens in Zimbabwe are encouraged to shelter in place until further notice,” the embassy said in a statement posted on its website.
The embassy added that diplomatic employees had been advised to remain at home on Wednesday due to “ongoing political uncertainty through the night”.
“US government personnel have been instructed to shelter in their residences tonight and work remotely from home on 15 November. The embassy will be minimally staffed and closed to the public,” the statement said.
The country has plunged into unrest since a top military official warned he might need to “step in” to halt the expulsion of supporters of former Vice President Emmerson Mnangagwa. Soldiers reportedly fanned out across Harare and took control of a state broadcaster. Reuters reported multiple explosions being heard and tanks were seen rumbling into the capital.
Mr Mnangagwa was in line to take over for longstanding President Robert Mugabe but was pushed aside as Mr Mugabe elevated his wife Grace Mugabe.
Army tanks wait just outside of Zimbabwe capital
The battle over who would succeed Mr Mugabe reflects the perilous road ahead as Zimbabwe contemplates another leader for the first time in decades.
The 93-year-old Mr Mugabe has ruled Zimbabwe for decades. His reputation as a lion of the African post-colonial independence movement has been tarnished by accusations of human rights abuses.