SEOUL, South Korea - It's not just about beef anymore.

As tens of thousands waved candles in central Seoul and other South Korean cities, a month of street demonstrations against the purported danger of U.S. beef broadened last night into a populist backlash against the country's fledgling president, Lee Myung Bak.

Lee's entire cabinet offered to resign early yesterday to take responsibility for the beef dispute and to take heat off Lee, who has been in office less than four months.

The offer came in anticipation of what was by far the biggest night of demonstrations against his government.

Chanting "Out with President Lee" and wearing stickers that made Lee look like a rat, the crowd included office workers, parents with children, college students, and labor groups.

"It is too late to soothe the public with lip service, and even fixing the beef issue is too late," protester Lee Hong Taek said. "The real question is his leadership style."

Police said 70,000 people protested in Seoul; organizers put the number at 700,000. Local media estimates ranged from 400,000 to 600,000.

Despite repeated assurances from Lee's government and the United States, many South Koreans still fear that U.S. beef would infect them with mad cow disease.

But people in the streets are also angry about what they call Lee's arbitrary way of making major decisions, his tone-deaf response to public opinion, and his choices of rich and, in some cases, unsavory business leaders for senior government positions.

"The president must realize that this is a very serious situation," said Kim Hyung Suk, 60, the owner of an after-school institute. "If he does not listen even now, then the next step is to demand that he steps down."

Soaring oil prices have also soured the public mood, and truckers voted Monday to strike for cheaper fuel, even after Lee's government offered a $10.2 billion package of aid that would provide some subsidies for gasoline and diesel fuel.

The offer by his cabinet to resign may give Lee an opportunity to appease populist anger, rebuild his government, and recast his image.

Lee, 66, a former construction-company executive, has stumbled badly in his first 107 days in office. He won election last fall by the largest margin in South Korean history, but his approval ratings have fallen below 20 percent.

In April, Lee stunned many by lifting the 41/2-year ban on U.S. beef that was put in place after a dairy cow in Washington state was confirmed as the first case of mad cow disease in the United States.

After his poll numbers collapsed and street demonstrations gathered support, Lee last week changed course and reimposed part of the beef ban. But that has done little to appease protesters.

Late yesterday, about 500 students turned up in front of the ruling party's building and threw raw eggs.

A presidential spokesman did not say whether Lee would accept the resignations of Prime Minister Han Seung-soo and 15 cabinet ministers.