South Korean police refused to allow more candlelight protests against the resumption of American beef imports, after the government announced Sunday it would not tolerate violent, illegal rallies.

Authorities used police buses to encircle a plaza in front of Seoul City Hall — the main site for weeks of evening rallies — to prevent protesters from gathering.

Nevertheless, about 1,700 people marched into nearby downtown streets chanting slogans demanding the government of President Lee Myung-bak cancel its decision to lift a ban on U.S. beef. Thousands of riot police quickly chased them away. There were no immediate reports of serious injuries or clashes.

The hard-line stance came hours after about 15,000 people — some wielding steel pipes and hurling stones at police — demonstrated in the capital, leaving several hundred injured.

The rally turned violent after some protesters used ropes to try to drag away police buses used as barricades to prevent them from marching into the presidential Blue House. Riot police immediately fired water cannons and sprayed fire extinguishers to repel them.

Angry protesters attacked police with steel pipes and stones, while police used clubs and shields against the crowd.

Justice Minister Kim Kyung-han said authorities may have no choice but to use measures such as tear gas to prevent clashes between police and protesters. Tear gas has been banned since 1999.

He also said authorities would arrest those who instigate violent protests, which he said would aggravate national economic difficulties amid rising global oil prices.

Rallies after sunset without police permission are officially illegal. Activists have nonetheless staged daily candlelight rallies to voice fears about the possible health risks of U.S. beef, such as mad cow disease. As officials began inspecting U.S. beef on Friday before it can reach markets, hundreds of labor activists blocked customs storage facilities.

"We are just here to express our opinions. I can't understand why this government tries to ban our rally," said Kim In-seok, 69, who runs a small construction company in Seoul. "Lee Myung-bak will face a serious public backlash."

U.S. beef has been banned for most of the time since late 2003, when the first case of mad cow disease in the U.S. was discovered. In the wake of public outrage over plans to resume shipments of American beef, the South Korean Cabinet offered to resign and the president reshuffled top advisers.

Earlier rallies opposing the beef import deal drew up to 80,000 people, but have since dwindled.

Jang Dae-hyun, a spokesman for the protest group, said police should cease harsh methods against demonstrators to prevent further violence. "We've been supporting peaceful rallies, but the police crackdown is too harsh," Jang said.