TOKYO (REUTERS) - Japan's embassy in South Korea has begun posting data on its website to show there is little difference in radiation levels between the two countries, in its latest retort in a diplomatic and trade row rooted in wartime history.

South Korea said last month that it will double the radiation testing of some Japanese food exports due to potential contamination from the tsunami-damaged Fukushima nuclear plant.

The embassy said the radiation reading in Seoul as of last Friday (Sept 27) was 0.12 microsieverts per hour, around the same as 0.135 in Fukushima City, and higher than Tokyo's 0.036. It will update the data every day the embassy is open, it said.

The World Nuclear Association has said the global average of naturally occurring background radiation is a range of around 0.17-0.39 microsieverts per hour.

"The Japanese government intends to continue providing accurate information based on scientific evidence, and to communicate carefully and transparently," the embassy website said.

"We hope that the Korean people will better understand Japan's radiation levels."

Relations between South Korea and Japan began deteriorating late last year following disagreements over compensation for forced labourers during Japan's occupation of Korea.

That escalated into a trade row this year as Japan tightened its curbs on exports of high-tech materials vital to South Korea's chip industry.