About 100,000 flag-waving South Koreans marched with candles in downtown Seoul in the biggest protest yet over the impending resumption of US beef imports Tuesday while police guarded the presidential office with a giant barricade.

Shouting, "Renegotiate"!, the demonstrators took part in Tuesday's candlelit protests. Some 20,000 riot police were being mobilized. The South Korea's largest candlelight rally was held in Seoul to pressure the Lee Myung-bak administration to renegotiate an agreement to open South Korea's market to US beef with almost no restrictions.

Protesters rally on a street leading to the US embassy and the presidential Blue House in central Seoul June 10, 2008. (Xinhua/Reuters Photo)

The entire cabinet earlier offered to quit to take responsibility for weeks of turmoil over the deal, which opponents say exposes South Koreans to the risk of mad cow disease.

A presidential spokesman said no decision had been made yet about ministerial changes and the current cabinet would stay in office for the time.

Police went on the highest alert, erecting a giant barricade at the protest venue. The 5.5-meter high barricade, built with dozens of 4-ton containers, completely blocked the Gwanghwamun street adjacent to the US Embassy, just about one kilometer away from the presidential office of Cheong Wa Dae.