A raging inferno that ripped through a forest in the Chernobyl exclusion zone and threatened to pose a serious radiation risk has been contained, Ukrainian officials said on Tuesday.

The blaze, which started 11 days ago when dry grass was being burnt, is almost extinguished with "no open fire" left, only "smouldering" parts, emergency services confirmed.

Hundreds of firemen, helicopters and planes were deployed to fight the flames. Almost 538 tons of water were dropped from aircraft on Monday. Experts and environmental activists expressed fears that the fire could lead to a hike in radiation at the site of the world's worst nuclear accident.

Sergiy Zibtsev, head of the Regional Eastern European Fire Monitoring Center, warned that the fire had become "super-huge" and "unpredictable".

Chernobyl tour operator Yaroslav Yemelianenko, in a Facebook post, described the situation as critical, saying the fire had reached the abandoned city of Pripyat, only two kilometers from where "the most highly active radiation waste of the whole Chernobyl zone is located."

Ukrainian authorities, however, claimed that only short-term spikes in Caesium-137 particles were noticed in and around the Kyiv area, south of the plant and that overall radiation limits remained within usual parameters.

In a statement, president Volodymyr Zelensky vowed to ensure transparency: "Society must know the truth and be safe." Zelensky is expected to meet the head of the emergency services to discuss the event.

The fire began on 3 April after an unusual spell of dry weather in the western part of the exclusion zone and rapidly spread to adjoining forest areas. The police have identified a local man who they think might have deliberately started the blaze. It is yet to be established if the 27-year-old suspect, who reportedly confessed to igniting a number of fires "for fun," is solely responsible for the latest incident.

A massive explosion and fire at the fourth reactor of the Chernobyl nuclear power plant in April 1986 had polluted large swathes of Europe. It forced the displacement of thousands of people from Pripyat, now a ghost city, situated near the power station. The three other reactors at Chernobyl continued to generate electricity until the facility was finally closed in 2000. A giant protective dome was installed over the fourth reactor in 2016.

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