Seoul - Ten of thousands of South Korean auto workers went on a partial strike Wednesday to protest the government's lifting a ban on importing US beef.

A spokesman for Hyundai, the country's largest carmaker, said said 44,000 workers would strike for two hours during both the day and night shifts at four factories.

At affiliate Kia Motors up to 20,00 workers are expected to stop working for two hours.

The strike was called by the Korean Confederation of Trade Unions (KCTU) over a new import deal that allowed US beef to be sold Tuesday in South Korea for the first time since imports were halted in 2003 after a US mad cow case.

Since an April agreement to lift the ban there have been mass rallies nationwide. The crisis has caused President Lee Myung Bak's approval ratings to plummet and there have been calls for the resignation of the new leader, who took office in February. His cabinet, however, offered to quit en masse.

Last week the two countries agreed on more stringent import criteria that only beef younger than 30 months would be allowed into South Korea. Mad-cow disease occurs mainly in older cattle.

The removal of the import ban was considered a condition for the ratification of a South Korean-US free trade agreement by the US Congress.

Mad-cow disease, or bovine spongiform encephalopathy, is a brain-wasting illness that can be transmitted to people who eat infected meat. (dpa)