A visit to Harare's largest hospital Parirenyatwa on Tuesday showed most units were being manned by a skeletal staff of senior nurses and doctors, with the aid of student nurses.
There was no sign of activity in the out-patients unit.
The official Herald newspaper said the strike had also virtually paralysed operations at Harare Central Hospital, as well as Mpilo and United Bulawayo hospitals in Zimbabwe's second city of Bulawayo.
Doctors who earn between Z$263,305 and Z$807,735 a month (about US$48 and US$147 at black market rates) want their salaries raised to Z$30 million, citing inflation which has surged to nearly 460%.
On Tuesday, state radio quoted Health Minister David Parirenyatwa as saying the strike was illegal because doctors and nurses were classified as providing essential services and barred from job boycotts.
Zimbabwe has seen a series of strikes by government workers over the last two years as the country grapples with an economic crisis.
Chronic food and foreign currency shortages, record unemployment of more than 70% and one of the highest rates of inflation in the world confront the country.
Critics say Mugabe, in power since independence from Britain in 1980, has ruined the economy through mismanagement.
But the veteran leader blames the malaise on sabotage by his local and international opponents, angry over his seizure of white-owned farms for redistribution to landless blacks.