Fire has engulfed a large section of woods in the exclusion zone around the destroyed Chornobyl nuclear power plant.
Ukrainian Prime Minister Arseniy Yatsenyuk says the fire is being brought under control.
Earlier, the Interior Ministry warned that high winds were blowing the fire in northern Ukraine toward Chornobyl, where in 1986 a reactor explosion and fire led to the world's worst civilian nuclear disaster.
Interior Minister Arsen Avakov said the fire involved about 400 hectares.
It is unclear if the fire has hit parts of the zone heavily contaminated by radiation from the 1986 accident.
A 30-kilometer zone around the plant is off-limits to most people except for workers constructing a new shelter to cover the destroyed reactor's building, and to visitors on short trips.
Based on reporting by Reuters and AP