Sunday's labour rally ended in violence

It follows violent protests at the weekend by supporters of the Korean Confederation of Trade Unions (KCTU).

The South Korean President, Roh Moo-hyun, has appealed for calm.

The KCTU is calling on the president, a former labour lawyer, to repeal laws that allow union leaders to be sued for lost production during strikes.

The umbrella labour group said that in addition to the strike, 10,000 unionists would protest near parliament in defiance of police refusal to allow a rally.

About 35,000 workers took part in protests on Sunday, which turned violent when the demonstrators hurled fire bombs at riot police.

The police said at least 44 officers were wounded, while union leaders said 100 workers were hurt, 56 seriously.

Police said they had summoned KCTU Chairman Tan Byung-ho and five other union leaders to appear for questioning by Thursday over the rally, but a KCTU spokesman said the union would ignore the police summons.

"Tan will not go to the police because he didn't do anything wrong," the spokesman said.

The workers at Sunday's strike said they were out to avenge three colleagues who killed themselves in recent weeks in protest against government policies.

Some, wearing mourning dress, marched with pictures of the dead union leaders.

Others waved red and white flags and banners, including one that read "No more killing".

Our correspondent in Seoul, Charles Scanlon, says the KCTU has become frustrated with the policies of President Roh, who has recently taken a harder line against unionists following a series of damaging strikes at some of South Korea's leading companies.

Mr Roh granted wage and working hour concessions to strikers following a long hot summer of labour action, but 132 unionists were arrested and unions have been sued for 140bn won ($118.6m) in strike damages.