Militant protesters blocked trucks from leaving warehouses for a second day on Friday as South Korea resumed quarantine checks on U.S. beef imports, moving to bring the product to market for the first time in nine months.
South Korea allowed the resumption of the imports on Thursday under a deal that has caused a crisis for the new government of President Lee Myung-bak, delaying pro-business reforms for Asia's fourth-largest economy.
Police used water canon to stop some protesters, waving banners saying "No mad cow! Renegotiate the deal! Lee Myung-bak Out!", from trying to climb over a police bus.
Some 5,300 tons of U.S. beef that has been in deep-freeze storage in South Korea since October can now be inspected immediately and head to stores as early as next week.
"Five importers have requested inspection checks on 13 shipments and the inspection process, which takes between three to 18 days, started today," an official at the National Veterinary Research and Quarantine Service said.
As members of a militant union group blocked trucks, several thousand took to the street in central Seoul in what has become a nightly ritual of rallies against Lee's government.
"We'll send more people to warehouses where inspection is set to take place," said a statement from the Korea Confederation of Trade Union, which is holding a 48-hour strike to block beef shipments from moving out of warehouses.
South Korea, which banned imports of U.S. beef in 2003 after an outbreak of mad cow disease, briefly allowed in boneless meat from cattle under 30 months old last year but suspended imports after prohibited material was found in shipments.
When it agreed with the United States in April to allow in all cuts of U.S. beef regardless of the age of the cattle, South Koreans took to the streets by the tens of thousands, saying the pack opened the way for potentially dangerous products.
U.S. and South Korean officials insisted U.S. beef was safe but still reworked their deal at the weekend to limit trade to cattle under 30 months of age, thought to pose less of a risk of mad cow disease.
South Korean officials said the reworked pact would increase safety checks on U.S. beef, but violent protests erupted after the reworked deal was announced.
Lee, who scored a landslide victory in a December election, has seen his popularity plummet after his government signed the beef deal in April.