Radiation levels near the Chernobyl nuclear power plant have spiked as Ukrainian firefighters battle a nearby forest fire.

Key points: Two fires flared near the site at the weekend

Two fires flared near the site at the weekend Radiation levels in the area substantially exceeded normal levels

Radiation levels in the area substantially exceeded normal levels The zone is largely unpopulated, with only around 200 inhabitants

Two blazes erupted on Saturday inside the zone that was sealed off after the 1986 explosion at the plant.

Firefighters said the smaller blaze had been put out but the second one was still burning over about 20 hectares.

They said they were using aircraft to extinguish the blaze.

Authorities said radiation levels in the area substantially exceeded normal levels. Radiation levels in the capital Kiev, about 100 kilometres south, were within the normal range.

Police have reportedly tracked down a person suspected of starting the blaze. ( AP: Yaroslav Yemelianenko )

The 2,600-square-kilometre Chernobyl Exclusion Zone was established after the April 1986 disaster at the plant sent a cloud of radioactive fallout over much of Europe.

The zone is largely unpopulated, although about 200 people have remained despite orders to leave.

Blazes in the area have been a regular occurrence: some start when residents set dry grass on fire in the early spring, a widespread practice in Ukraine, Russia and some other ex-Soviet nations, that often leads to devastating forest fires.

Police said they tracked down a person suspected of starting the blaze.

They said the 27-year-old man said he burned grass "for fun", and then failed to extinguish the fire when the wind caused it to expand quickly.

Fires are common in the forest near the disused nuclear plant. ( AP: Yaroslav Yemelianenko )

Chernobyl polluted a large area of Europe when its fourth reactor exploded in April 1986, with the region immediately around the power plant the worst affected.

People are not allowed to live within 30 kilometres of the power station.

The three other reactors at Chernobyl continued to generate electricity until the power station finally closed in 2000. A giant protective dome was put in place over the fourth reactor in 2016.

AP