KIEV, Ukraine (AP) _ Radiation levels around the Chernobyl nuclear plant rose as much as tenfold after fires swept through nearby villages, but officials on Wednesday played down the potential health hazards.

Environmentalists expressed skepticism at the measurements, and criticized the Ukrainian government for not ordering tests in populated areas outside the 18-mile exclusion zone around the plant.

The fires on Tuesday, six miles northwest of the plant, revived Ukrainians' fears about lingering contamination from Chernobyl, where a reactor exploded and caught fire in the world's worst commercial nuclear disaster 10 years ago this Friday.

Flames raced through five contaminated, deserted villages for seven hours. On Wednesday, forest fires caused by unseasonably hot, dry weather engulfed areas of neighboring Belarus also contaminated by the 1986 blast.

After monitoring radiation levels in the exclusion zone, officials reported a four- to tenfold increase in the radiation from cesium in certain areas. The overall increase in the zone was 10 percent.

``But it's impossible to talk of an increase in the average dose to people, because the radiation background would have had to increase 1,000 times to reach what we call dangerous limits,'' said Yuri Ivanov, head of the radiation monitoring center for the exclusion zone.

Environmentalists said the government should also have tested radiation levels outside the zone.

``You have to be very careful with their figures,'' said Yevhen Kobetsky, a nuclear physicist who works with the Ukrainian environmental group Union to Save Chernobyl.

He was particularly concerned about the radiation doses received by the firefighters and the picnicking families who had returned to their former villages when the fire broke out Tuesday.

One of them is suspected of dropping a cigarette that started the fires, which spread quickly among dry pines and abandoned homes in one of the most heavily contaminated areas.

The families were not tested.

Some experts said the health danger from Tuesday's fire is probably minimal, because the leftover radioactive cesium is mostly in the soil, and would be unlikely to be wafted up by smoke from burning trees and buildings. But others insist that any increase in radiation is a threat.

``Any fire that size is certain to affect radiation levels,'' said Oleh Bykov, spokesman for Ukraine's civilian defense service.

For many Ukrainians, memories of the disinformation by the Soviet government after the 1986 accident run deep. Authorities did not initially report that accident, which caused at least 32 deaths and exposed 5 million people to radiation.

``I don't believe the official information that everything is fine here,'' said Alla Kulishova, 32, a saleswoman in Kiev, 70 miles to the south. ``Of course that's what they'll say. But I feel this danger everywhere.''

``When I heard about the fire my skin froze,'' she said.

Yelena Bondarenko, a businesswoman with two children, called for the immediate closing of the plant and cleansing of the contaminated regions.

``I understand (Ukraine) is very poor,'' she said. ``But when poverty hits a home, everyone makes a contribution to solving the problem. Let it be Western money or ours; I don't care. The zone should be clean.''

The West has long pushed for Ukraine to close Chernobyl, but the energy-starved former Soviet republic says it needs the electricity and jobs the plant provides. Two of the plant's four reactors are still operating.

The Group of Seven industrialized nations has pledged $3.1 billion to help shut the plant, but has not agreed on a timetable for dispensing the funds.