The health ministry raised the confirmed death toll from seven to nine just a day after the WHO urged the country to report all cases over fears transmission may be more widespread.
The ministry tweeted there were a further 13 positive cases, two of whom had been hospitalized and another who had recovered while "a total of 825 contacts have been followed up."
The WHO has warned of a potential large scale epidemic which could spread to neighboring Gabon and Cameroon.
The outbreak of the hemorrhagic fever has spread beyond the province of Kie-Ntem, where it caused the first known deaths in January and reached Bata, the economic capital of the west African nation.
The reported cases are in three provinces 150 kilometers apart, "suggesting wider transmission of the virus", said WHO chief Tedros Adhanom Ghebreyesus on Wednesday.
On March 22, WHO Africa regional headquarters said it knew of 20 further probable cases, all of whom were dead and the organization's alert and response director Abdi Mahamud noted "signs of the wide spread of transmission that are making us (worried)."
Tanzania announced last week five deaths from Marburg, but insisted it has the spread under control after sending a rapid response team to the northwestern region of Kagera which borders Uganda.
The Marburg virus causes severe fever, often accompanied by bleeding and organ failure.
It is part of the so-called filovirus family that also includes Ebola, 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.
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 being evaluated.
