Hungary was the latest European country on Saturday to confirm higher than usual levels of radioactivity in the air, although like others it maintained that this did not pose any health risks.

"In Hungary, a higher-than-usual concentration of iodine-131 particles was registered in Budapest and Miskolc (in the northeast)," Geza Safrany, the head of the national research institute for radiology OSSKI, said in a statement.

He added that the increase was very slight and did not pose any health risk.

What lay behind this elevated radioactivity is still unclear, he also said.

On Friday, the UN atomic watchdog in Vienna said it had received information from Czech authorities that "very low levels of iodine-131" had been detected in recent days in the air in the Czech Republic and in other countries.

Poland, Slovakia and Austria quickly confirmed they too had detected abnormal levels in the last few weeks.

The International Atomic Energy Agency (IAEA) said however it did not believe this presented any risk to human health nor that it was caused by the nuclear disaster at Japan's Fukushima plant earlier this year.

In Poland, a spokesman for the atomic energy agency told AFP that the cause may lie in Pakistan, where officials were forced to repair a leak at the nearly 40-year-old Karachi Nuclear Power Plant (KANUPP) on October 19.

After the incident, an official from KANUPP had told AFP that no radioactivity had been recorded and none of their staff had been affected.

The Vienna-based agency said Friday it was working with its counterparts to determine the cause and origin of the iodine-131, which has a half-life of around eight days, and that it would provide further information as it became available.