BEIJING -- China's seawater, as a source of salt, would not be affected by radioactive leaks following explosions at the Fukushima Dai-Ichi nuclear power plant in Japan, said the country's marine environment watchdog Thursday amid a salt panic among the public.

The National Marine Environmental Forecasting Center said in a statement that currents in the Pacific Ocean out from Fukushima were flowing west to east, while China is located to the west of Japan.

"It is impossible for radioactive substances to reach China's sea areas via the ocean current," the statement said.

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Also, China has huge salt reserves and over 80 percent of the salt comes from inland areas. The public need not panic and hoard salt, the statement noted.

Supermarkets in many Chinese cities have run out of salt as a wave of panic buying spread from east China's Zhejiang Province Thursday afternoon to Guangdong, Jiangxi, Guizhou, Sichuan, Jiangsu and Hubei provinces as well as the municipalities of Beijing and Chongqing.

Rumors in some Chinese cities say that radiation has leaked into the sea from the Fukushima nuclear power plant, compromising the safety of salt taken from the sea in the future.

Another reason people have rushed to buy is that salt with iodine is believed to help protect people from the effects of nuclear radiation.

Su Xu, a researcher with the Chinese Center for Disease Control and Prevention, said that iodized salt would do little to protect against radiation, as the iodine content in salt is much less than that in the iodine tablets, which could be taken to reduce the impact of possible radioactivity.

Su also warned that taking excessive amounts of iodine was harmful to health, saying that iodine drugs should only be prescribed by doctors and medicine specialists.

Latest air monitoring results by 11 a.m. Thursday showed that China remained unaffected by the radioactive leaks, according to the National Nuclear Safety Administration, under China's Ministry of Environmental Protection.