South Korean police broke through barriers set up by Daewoo Motor workers today. One report said some leaders of a protest over layoffs at the automaker's main plant had been arrested.
"The situation will be under control shortly," a spokesman at Pupyong district police said.
Yonhap News reported some trade union leaders were arrested but union officials were not immediately available for comment.
South Korea's third-ranked car-maker went bankrupt last year.
Witnesses said fleeing workers and members of their families - who had occupied the plant in Pupyong east of Seoul over the weekend - threw petrol bombs at the advancing police.
Fire engines and ambulances rushed to the plant soon after police went in just after 6 p.m. (9 a.m. British time).
Some 2,000 riot police clashed with around 300 workers repeatedly today in a battle of metal pipes and water cannons sparked by the layoff of 1,750 workers on Friday.
Earlier four injured Daewoo workers were rushed to hospital, witnesses said.