South Korea's government has issued a stern warning in reaction to Saturday night protests that left more than 100 people injured. Officials say police will take every necessary measure to track down violent protesters, and will consider resuming the use of tear gas for the first time in nearly a decade. VOA's Kurt Achin has more from Seoul.

South Korean officials say illegal and violent protests over the resumption of U.S. beef imports will no longer be tolerated.

Saturday's day-long protest escalated into clashes between police and demonstrators by nightfall. Police say the demonstrators vandalized buses authorities had set up as barricades. Authorities say some of the protesters attacked by throwing stones, swinging steel pipes, and even shooting acid from squirt guns at police. More than 50 protesters were taken into custody.

South Korean Justice Minister Kim Kyung-han read a formal statement of warning from the government that those inciting violence would be punished.

He says the government is determined to thoroughly track down anybody who assaults police and either plans or carries out violent acts, and to punish them severely. He says the government will also sue rioters for damages to public property.

This weekend's demonstrations follow about two months of almost nightly street protest over South Korean President Lee Myung-bak's April deal to resume U.S. beef imports. Many South Koreans are convinced U.S. beef poses a risk of transmitting the brain-wasting mad cow disease to humans.

Mr. Lee's political opponents have paralyzed the legislature for weeks with a boycott. Parts of downtown Seoul have become nearly impassable with the demonstrations, and are littered with spray-painted shells of police buses with slashed tires.

The street demonstrations reached a peak on June tenth, when about 100-thousand people turned out to air a host of grievances against President Lee beyond just the beef import issue. Since then, Mr. Lee has apologized twice to the nation and amended the controversial beef deal.

The protesters have dwindled in numbers, but become more aggressive-- most of them affiliated with miltiant trade unions. The protesters argue they are responding to excessive use of force by South Korean police.

Justice Minister Kim, speaking on behalf of several South Korean ministries, warned future violent protests would be countered by "all legally available means," including the use of tear gas. South Korean law enforcers have refrained from using that since 1999.