An environmental activist wears a mask, as part of a rally to protest the building of more nuclear plants in South Korea, in Seoul March 29, 2011.[Photo/Agencies]

SEOUL -- Traces of radioactive iodine have been detected in Seoul, a state-run nuclear safety agency said Tuesday, a day after the government confirmed minuscule amounts of radioactive xenon-133 in the country's eastern province of Gangwon.

The Korea Institute of Nuclear Safety (KINS) said it had detected traces of iodine-131 in the atmosphere after analyzing air samples collected from its 12 radiation monitoring stations across the country, including Seoul.

The institute said in a statement the amounts were so small that there was no immediate risk to public health or the environment.

However, the public could not hide their growing worries about radiation contamination.

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"There is a rumor that foods can control (radiation poisoning), but I don't think there are definite countermeasures. I need to be cautious and watch the news carefully," said Kim Hye-sul, 51.

"Miniscule amounts do not pose immediate risk but problems may  happen in the next generation. Therefore, I think something must be done immediately," said Cho Ye-seul, 21.

The KINS assumed that the radioactive substance leaked from the stricken Fukushima nuclear power plant in Japan flew to the Kamchatka Peninsula in Russia, circled around the Arctic region and Siberia and moved to South Korea.

The Ministry of Education, Science and Technology said it began to collect air samples from its radiation detection stations across the country on a daily basis. Previously, it conducted the process once a week.

South Korea also plans to carry out extensive safety checks over the next month on all of its own 21 nuclear reactors, which produce 35 percent of the country's electricity.