The built-in bottom washers and pre-warmed seats of Japan's luxury toilets faced a storm in a U-bend on Thursday as Chinese state-run media launched a thunderous tirade against them.

The Global Times, which is affiliated with the Communist Party mouthpiece People's Daily, devoted the editorial in both its English and Chinese editions to the subject, under the headline: "Popularity of Japanese toilet seats overstated".

There were calls for Chinese consumers not to purchase Japanese goods when the two countries' relations reached crisis point over East China Sea islets controlled by Tokyo and claimed by Beijing.

Buying its neighbour's lavatories "makes a mockery of China's boycott of Japanese goods", the paper said.

"That Chinese tourists swamp Japanese stores at a time when the country is facing a sluggish domestic demand is certainly not something to be proud of," it said.

Both sides have repeatedly sent ships and aircraft to the islands, but despite their political differences Asia's two biggest economies have close business ties.

Roughly half a million Chinese tourists descended on Japan over this month's Lunar New Year holiday, spending an estimated $882 million according to Nomura Securities.

And AFP was able to confirm Thursday that the toilets at the foreign ministry in Beijing are manufactured by Japanese industry leader Toto -- although of the normal variety, rather than full-service models.

- Worshipping the great white altar -

A slight thaw in relations saw the two countries' leaders meet during a regional summit in November, but tensions remain high with many ordinary Chinese still resentful over Japan's invasion of China during the 1930s and 1940s, events state media and the Communist party regularly recall.

Japan's nationalist Prime Minister Shinzo Abe angered Beijing in 2013 by visiting Tokyo's Yasukuni Shrine, which honours Japan's war dead including convicted war criminals from World War II.

It was unclear why the Global Times focused its ire on the smallest room, but it may have been triggered by a Beijing Youth Daily article that said the seats were second only to rice cookers in popularity among purchases by Chinese tourists to Japan.

The high-tech bathroom accessories, often equipped with multiple water jets, hot air dryers and automatic lid raisers, are common throughout Japan but a dramatic contrast to the squat facilities still common in much of China.

Basic models cost around $200 but buying at the top of the range can mean flushing away thousands, and they are often seen as a status symbol among Chinese nouveau riche.

The Global Times acknowledged that the toilets' popularity "is not accidental as they explicitly show the human touch, intelligent design and sophistication of Japanese goods".

But it added with disdain: "World-class toilet seats are not what Chinese manufacturers aspire to make."

Many ordinary Chinese seized on the point, saying China should not care about simple household appliances and should instead strive to innovate.

"There is no need to revere a toilet seat on the level of a god," said a poster on the Global Times' Chinese website.

"We should be focusing on developing new heights in technology like robotics and microchips."

Many commenters adopted potty language, while others mocked the paper for giving such prominence to a toilet.

"Alert the people of this sinister Japanese plot! We must unite to walk our own path and our own national dream," said one, borrowing language frequently used in Communist Party slogans.