(Reuters) - The U.S. ambassador in Zimbabwe has instructed all employees to remain home on Wednesday due to  ongoing political uncertainty,  the embassy said in a statement on its website amid speculation about a coup.  U.S. citizens in Zimbabwe are encouraged to shelter in place until further notice,  the statement said, adding the embassy would be closed to the public on Wednesday. Soldiers deployed across the Zimbabwe capital Harare and seized the state broadcaster on Wednesday after 93-year-old President Robert Mugabe s ruling ZANU-PF party accused the head of the military of treason. 