TOKYO - Japanese angered at U.S. exports of corn contaminated by gene-spliced StarLink donned skull masks and black  cloaks to demonstrate outside the U.S. embassy in Tokyo on Wednesday, demanding tighter safety measures.

Consumer opposition to genetically modified (GM) crops has been growing since tests last month by a local consumer group revealed traces of unapproved StarLink in corn for food as well as for domestic animal feed.

Representatives of the Consumers Union of Japan and member of parliament Tomoko Nakagawa joined a group of several dozen protesters outside the embassy to protest against U.S. exports of the gene-spliced corn to Japan.

Waving white and yellow banners reading "No! StarLink Corn," the demonstrators dressed in black cloaks and white skull masks, demanded the U.S government call a halt to exports of U.S. corn commingled with StarLink.

Amagasa Keisuke, head of a campaign against GM food, called on the United States to stop the sale and export of GM products until it could guarantee to Japan that products would be free of StarLink through separate handling from the farm and along distribution channels.

NO GUINEA PIGS

"We don't want to eat GM corn," said one campaigner. "Don't treat us like guinea pigs."

In Japan, StarLink is not approved even for animal feed. StarLink, made by Franco-German life sciences firm Aventis SA , has not been approved for human consumption because StarLink, made by Franco-German life sciences firm Aventis SA , has not been approved for human consumption
because of U.S. regulators' concerns about potential allergic reactions.

After the consumer group's discovery of StarLink in a shipment from the United States last month, trade in Japan, the biggest U.S. corn export market, has ground to a virtual halt, with importers scrambling to find alternative supplies.

Japan's Agriculture Ministry said on Monday that 10 out of 15 samples of imported corn for animal feed obtained between April and June this year were found to be contaminated with StarLink.

Late last week, the ministry began its own feed on poultry using StarLink corn to assess the safety for animal feed. The tests would take three months.  This month, the Health Ministry agreed to a U.S. testing plan to prevent StarLink corn from tainting exports to Japan for direct human consumption.  Japanese importers fear the U.S. plan falls short of full safety assurances and local food and feed industries are reluctant to pay the extra cost for tests, traders said.

Most Japanese importers appear unlikely to resume purchases of U.S. corn until queries about StarLink corn have been answered.

Traders said on Tuesday Japan had signed deals to buy possibly as much as 200,000 tonnes of Chinese corn for November and December shipment.

The StarLink issue has deepened concerns about the U.S. ability to comply with Japanese legislation to be implemented from next April that will set zero tolerance for imports of unapproved genetically modified products.  Japan imports about four million tonnes of corn for food per year and another 12 million tonnes for animal feed, mostly from the United States.