The Ukrainian National Guard has been put on high alert due to worsening forest fires around the crippled Chernobyl nuclear power plant, according to Ukraine Interior Minister Arsen Avakov.

"The forest fire situation around the Chernobyl power plant has worsened," a statement on Avakov's Facebook page says.

"The forest fire is heading in the direction of Chernobyl's installations. Treetop flames and strong gusts of wind have created a real danger of the fire spreading to an area within 20 kilometers of the power plant. There are about 400 hectares [988 acres] of forests in the endangered area."

Police and National Guard units are on high alert. Ukraine’s Prime Minister personally went to the affected area to oversee the firefighting. He says the situation is under control, “but this is the biggest fire since 1992.”

However, in comments to Russia’s Moscow Speaks radio, a representative of Greenpeace Russia said that the situation is much worse: “A very large, catastrophic forest fire is taking place in a 30-km zone around the Chernobyl power plant. We estimate the real area of the fire to be 10,000 hectares; this is based on satellite images. This hasn't been officially acknowledged yet.”

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The potential danger in this fire comes from the radioactive contaminants the burning plants have absorbed, ecologist Christopher Busby told RT. “Some of the materials that were contaminating that area would ahve been incorporated into the woods. In other words, they land on the ground in 1986 and they get absorbed into the trees and all the biosphere. And when it burns, they just become re-suspended. It's like Chernobyl all over again. All of that material that fell on the ground will now be burned up into the air and will become available for people to breathe." Christopher Busby is the scientific secretary of the European Committee on Radiation Risks.

Ecologist Dmitry Shevchenko from the Environmental Watch on North Caucasus says it is difficult to predict where exactly the contaminants will go: “We don't have a real-time monitoring system for the Chernobyl area. We can hypothesize whether the radionuclides will go here or there, but there is no-one who can reliably predict the situation."

Ukrainian emergency services say 182 people and 34 vehicles have been dispatched to fight the fire. A Mi-8 helicopter and three An-32 water dropping airplanes are also working at the scene. The efforts are being coordinated from a mobile emergency headquarters.

According to the head of the Chernobyl Exclusion Zone management department, radiation levels in the area remain normal. “The area on fire is relatively clean,” Vasily Zolotoverkh told the newspaper kp.ua. He said the fire started at lunchtime, when emergency workers had finished putting out an earlier blaze which started during the night. The emergency services have stated that it could have been caused by a lit cigarette.

Ukraine's acting head of emergency services said earlier the forest fires were not a threat to the sarcophagus sealing off Chernobyl's crippled Reactor 4.

Chernobyl and the surrounding area have been abandoned and remain off-limits following the April 1986 disaster, when an explosion and fire released massive amounts of radioactive material into the atmosphere. Increased radiation levels were detected throughout Europe.

Chernobyl became the worst nuclear disaster in world history in terms of casualties and clean-up costs. Reactor 4, where the blast took place, was sealed off in a giant reinforced concrete sarcophagus to prevent further leaks.