"Our public health laboratory results have confirmed that this disease is caused by Marburg virus," Health Minister Ummy Mwalimu said, urging citizens to remain calm "as the government has managed to control the spread of the disease."
Three patients are receiving treatment in hospital and 161 contacts are being traced by the authorities, she added.
"There is no need to panic or stop economic activities as Tanzania is not the first. We have all we need to control the infectious disease," Mwalimu said.
The Marburg virus is a highly dangerous microbe which causes severe fever, often accompanied by bleeding and organ failure.
It is part of the so-called filovirus family that also includes the Ebola virus, which has wreaked havoc in several previous outbreaks in Africa.
The suspected natural source of the Marburg virus is the African fruit bat, which carries the pathogen but does not fall sick from it.
The animals can pass the virus to primates in close proximity, including humans, and human-to-human transmission then occurs through contact with blood or other body fluids.
Fatality rates in confirmed cases have ranged from 24 percent to 88 percent in previous outbreaks, depending on the virus strain and case management, according to the UN's World Health Organization (WHO).
There are currently no vaccines or antiviral treatments, but potential treatments, including blood products, immune therapies and drug therapies, as well as early candidate vaccines are being evaluated, the WHO says.
Eleven people died in the West African state of Equatorial Guinea, in an outbreak first documented on January 7.
Marburg Fingered in Tanzania Fatalities
DAR ES SALAAM - A mysterious disease that killed five people in Tanzania has been identified as Marburg hemorrhagic fever, a cousin of Ebola, the health ministry said Tuesday.