The fires threatened 22 settlements and engulfed an area of about 9,300 hectares (36 square miles), the service said in a statement, adding that 120 people had been evacuated.
Local authorities said there were a total of 146 fires, 82 of which had been extinguished.
Local Ukrainian authorities have said the fires may have been caused by shelling from a nearby area that is controlled by pro-Russian forces, a crossing point to which was closed due to the fire.
The office of Ukraine's president called on law enforcement bodies to find the cause of the fires, saying: "The reasons for such a large-scale spread of fire must be clearly established."
"We also take into account the information about provocative shelling that could have been carried out from the temporarily occupied territory ... and could have caused at least some of these fires in such weather conditions," it said in a statement.