The militant Korean Confederation of Trade Unions (KCTU) has said it hoped for an end to the strike wave before the 31 May start of the football tournament, which South Korea is co-hosting.

But union chiefs said they would not capitulate merely to save the country international embarrassment.

"If some employers think that our movement will be discouraged in the run-up to the World Cup and do not negotiate seriously, we will carry out the protest despite the soccer tournament," the union said on Monday.

Tough stance

"We will stage more concerted industrial action in early June if employers use the World Cup to reject our demands."

Union chiefs have accused the government, which has banned demonstrations near the 10 World Cup venues, of using the tournament as an excuse to launch a labour crackdown.

Industrial action began last week when workers at metals and chemicals plants walked out in support of demands for higher pay and shorter working hours.

The strike spread to workers including taxi drivers and hospital staff, with union organisers claiming that about 40,000 employees took part in Thursday's protests.

Dispute set to spread

While some taxi drivers and hospital unions have reached wage agreements, the KCTU said industrial action could intensify from Wednesday when metal workers are set to start an all-out stoppage.

Subway workers and KCTU members in telecoms firms are set to strike on Tuesday, with taxi drivers threatening to hold a rally on Thursday.

But government officials, estimating that 22,400 KCTU members at 67 firms were on strike on Monday, said the protests were fizzling out.

"With labour bargaining at firms being settled, the KCTU-led strike fever shows a sign of wilting," an official spokesman said.