Firefighters in Ukraine are trying to prevent the country's largest forest fire in decades from spreading towards the abandoned Chernobyl nuclear power plant.

A 30km exclusion zone remains in place around the plant, where in 1986 a reactor fire led to the world's worst nuclear disaster.

Earlier, the interior ministry warned that high winds were blowing the fire towards the abandoned area.

"The situation is being controlled, but this is the biggest fire since 1992. We've not had this scale of fire," a government spokesman said.

"It is around 20km (from the fire) to the plant."

"Our emergency services are actively working there to prevent the fire spreading further."

Earlier this year, international experts warned a large amount of dangerous isotopes remained in the forests near Chernobyl - which could be spread by fires.

"Wildfires...pose a high risk of redistributing radioactivity," according to a paper published in Ecological Monographs.

Chernobyl's Reactor 4, the epicentre of the 1986 blast, is covered with a concrete casement that the Ukrainian authorities plan to replace by 2016.