European countries have seen stocks of iodine fly off the shelves due to fears it may be needed to counter the risks of thyroid cancer if Russia's invasion of Ukraine causes a nuclear incident.

Health Minister Alexandru Rafila said the government would start distributing the tablets from next week through family doctors though he warned they should not be taken preventively.

"They should be taken if there is a nuclear incident in the vicinity. Otherwise, they should not be taken," he told reporters.

The ministry will also launch an information campaign to guide the population on how to obtain the pills, how to store them and how to administer them.

Rafila said a nuclear incident was "not probable" but "possible".

"We cannot absolutely rule it out... We have to prepare for such a situation," he said, adding the pills had a shelf-life of three years.

The war is the first to occur in a country with a vast nuclear estate comprising 15 reactors.

On March 4, Russian forces captured the Zaporizhzhia nuclear plant, Europe's largest, sparking alarm when shelling caused a fire at a training facility at the complex.

Ukraine's now defunct Chernobyl power plant was the site of the world's worst nuclear disaster when it exploded in 1986 killing hundreds and spreading a radioactive cloud across Europe.

Several doctors have warned of the dangers of taking iodine without proper precautions, pointing at the serious side effects.

International health authorities say the tablets must be taken at precise times just before or after exposure with an incident occurring within a distance of some 20 kilometres (12 miles).

They are recommended in particular for pregnant women, babies, children and young people.