SEOUL, June 8 (Xinhua) -- Thousands of Koreans scuffled with riot police in downtown Seoul until early Sunday morning as they tried to march on the presidential office Cheong Wa Dae to protest the U.S. beef import deal.

Protestors give bottles of water to riot policemen as they confront each other during a march toward the presidential Blue House in Seoul after a candle-light vigil June 7, 2008.(Xinhua/Reuters Photo) Photo Gallery>>>

    They were part of the approximately 40,000 protesters who marched in the city center carrying candles and chanting slogans calling for complete renegotiation of the deal for a stricter age limit despite Washington's pledge not to export beef from older cattle to help ease local fears over mad cow disease.

    President Lee Myung-bak called U.S. President George W. Bush on Saturday night (Seoul time) to ask for cooperation to ensure that U.S. beef from cattle older than 30 months of age, considered at greater risk of mad cow disease, is not exported to Korea, and Bush promised to do so, according to Lee's office.

    Some 8,800 protesters and thousands of police confronted each other at the Gwanghwamun intersection near the U.S. Embassy in Seoul, with many spraying fire extinguishers or hurling plastic water bottles at each other. Some demonstrators climbed onto the barricades of police buses demanding President Lee come to hear the people's angry voices.

    About 10 people suffered facial and head injuries in the clashes and 11 people were arrested for violence, according to the police.

    Instead of revising the April deal, the Lee administration is pushing to encourage the private sector to voluntarily ban imports of U.S. beef from cattle over 30 months old, which is known to have the greatest risk of transmitting mad cow disease to humans.

    But anti-government protesters say the administration's measures are not sufficient to protect the nation from mad cow disease, demanding a restriction of U.S. beef imports to boneless beef from cattle under 20 months old and a ban on all risk materials from cattle of all ages.