Scores of opposition Democratic Party (DP) lawmakers and officials have occupied a main parliamentary hall since mid-December to block a series of controversial bills, including one to ratify a free trade agreement signed with the US last year, that awaits ratification by legislatures.

About 150 unarmed security guards, acting on the speaker's order, have intermittently attempted to break up the sit-in since Saturday. Some protesters were frogmarched out but most others remained in place by linking arms.

The opposition, which has 83 seats in the 299-member legislature compared with the ruling Grand National Party (GNP)'s 172, says the Republic of Korea should not ratify the free trade pact before the US Congress does.

Opposition lawmakers and critics, including farmers who fear it will hit their jobs, insist that the deal be given another review.