SEOUL : South Korea's political turbulence over US beef imports showed no sign of abating Saturday as activists called for fresh protests and opposition parties vowed to continue a parliament boycott.

Calm returned Saturday to central Seoul where more than 50,000 people swarmed through the streets late Friday, carrying banners and candles and chanting slogans.

About 100 protesters continued their action over an intersection near Gwanghwa Gate on Saturday as others, exhausted from an overnight protest, were asleep in several tents pitched up on sidewalks.

Hundreds of riot police, who struggled until early Saturday against protesters attempting to march toward the presidential Blue House, were catching some sleep in their buses.

Police on Friday wielded shields and trained chemical fire extinguishers toward demonstrators, who were trying to push their way through row after row of officers blocking every access to the presidential palace.

Protesters tied a few police vehicles with ropes and pulled the vehicles away, momentarily making some clearings through a row of buses which had been parked across the street as a barricade.

They also sprayed slogans on the sides of many of the police buses, witnesses said.

The protest took place in the heart of the city, which is about a kilometre away from the Blue House. Another mass rally is due to take place in the same area late Saturday.

President Lee Myung-Bak's young administration is being rocked by mounting protests after Seoul lifted a ban on US beef imports on May 29, sparking fears of human infections of mad cow disease.

It has been forced to delay the planned resumption of beef imports and ask Washington not to export beef from cattle more than 30 months old, seen as more vulnerable to possible infection, to ease public anger.

Lee's popularity has taken a nosedive as expectations of a quick economic turnaround faded fast even though the former construction company CEO was elected on a promise to reactivate the economy.

He has also been criticised over a series of key government appointments and an ambitious cross-country canal project he is pushing which activists say would be an environmental disaster.

- AFP /ls