The decision was taken yesterday by President Alpha Conde, the statement said, after he met his counterpart from Sierra Leone, Ernest Bai Koroma.
Impoverished Guinea and its neighbours Sierra Leone and Liberia have registered more than 11,000 deaths since the epidemic flared up in December 2013.
Liberia was declared Ebola-free in May, but the virus continues to thrive in Sierra Leone and Guinea.
In August last year, Conde declared a health emergency for the whole of Guinea. Then on March 28, 2015, he decreed a "reinforced health emergency" for five provinces in the west and southwest of the West African country.
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No comment was available from the authorities in Sierra Leone on this evening.
According to the statement, the regions of Guinea concerned were Forecariah, Coyah, Dubreka, Boke, Kindia, Boffa, Fria and Conakry city -- three more than in the March decision.
The emergency measures included the temporary closure of hospitals and clinics where there have been cases of Ebola.
Anyone hiding the sick or moving bodies would be prosecuted for "endangering other people's lives".
Guinea is the original epicentre but the least-affected country in the current Ebola outbreak, the worst in history since the virus was first identified in 1976.
It is also in Guinea where the reaction to the fight against Ebola has been the most violent, with eight members of an outreach team killed last September by protesters who denied the existence of the virus as a "white conspiracy".