Seoul, Korea - South Korea's embattled President Lee Myung Bak ordered his cabinet on Tuesday to take stern action against violent protests over US beef imports.

Mr Lee made the statement as his agriculture minister, Chung Woon Chun, said the resumption of the imports could not be delayed any longer.

'The government must listen to voices critical of government policy. But demonstrations challenging our national identity or illegal violent protests must be sternly dealt with,' Mr Lee was quoted by his spokesman as saying.

But a protest coalition has dismissed the latest deal as insufficient and vowed to continue demonstrating for a full renegotiation.

Mr Chung told journalists the government had made 'all out efforts' to secure extra safeguards.

He declined to set a date for the announcement of new rules on imports.

'However, we cannot delay it any longer,' he added.

Some 100,000 people packed central Seoul in a peaceful June 10 demonstration.

Rallies since then have been far smaller but some have ended violently.

Hundreds of protesters pulled one police bus away from a barricade, smashed its windows and fought with riot police after a rally on Saturday night.

Dozens of people were slightly injured, according to police and witnesses.

Two people were injured on Monday night in a clash between liberal and conservative groups following a candlelight rally involving about 1,000 protesters.

About 190 policemen have been injured with 58 police buses damaged during the weeks of protests, according to official data.

'The government cannot but deal sternly with illegal demonstrations for the sake of our economy. It's time to stop candlelit rallies and go back to work,' Culture Minister Yu In Chon said in a statement.

In hopes of pushing ahead with a wider free trade deal, Seoul agreed in April to lift its ban on US beef imports.

But massive protests forced it to delay the resumption and to urge Washington not to export beef from cattle aged more than 30 months, which are seen as more susceptible to the disease.

The US government has agreed to run an age verification system.

The demonstrations sparked a political crisis for Mr Lee, who saw his popularity plummet below 20 per cent.

On Friday he replaced almost all his top aides in an attempt to make a fresh start after four months in office.

Media reports say Mr Lee may delay a planned cabinet reshuffle until after parliament starts sitting again.

The legislature has been paralysed by an opposition boycott over the beef issue. -- AFP