No radioactive iodine-131 has been detected in the air in Croatia, State Office for Radiological and Nuclear Safety announced after reports of contamination in several European states.

The UN atomic agency IAEA said "very low levels" of radioactive iodine-131 had been detected in the air in the Czech Republic and in other countries, but presented no risk to human health, AFP reported on Friday.

Poland, Slovakia and Austria also said that they had detected abnormal but still very low levels, with Poland saying they had been "100 times higher" in March after Japan's Fukushima nuclear accident.

The measured quantities of the radioactive substance are not harmful to human health.

The authorities are working on determining the source of the contamination, believed not to be related to Fukushima Daiichi nuclear accident in Japan eight months ago.

In Croatia, the measurements are conducted continuously in two locations – Sveti Kriz (north) and Batina (east).