Thousands of demonstrators marched outside Mongolian government headquarters Tuesday, burning effigies of the nation's leaders and demanding their resignations because of alleged corruption and the mishandling of mineral wealth.

Protest leaders also announced a hunger strike to demand a response to their grievances.

Some of the protesters have been camped in the city's central square for nearly two weeks. They are demanding that the three-month-old government resign if it cannot obtain favorable terms from Ivanhoe Mines Ltd. for the Canadian company's concession to mine a huge copper deposit in the southern Gobi region.

"Resign! Resign!" chanted a horseman dressed in an ancient warrior's costume as he circled the massive Government House, adjacent to the square.

An estimated 3,000 people were believed to have joined the protest. Hundreds of police guarded government offices, watching the protest without intervening.

The protesters burned effigies of President Nambaryn Enkhbayar, Prime Minister Mieagombo Enkhbold, the speaker of parliament and Robert Friedland, chairman of Ivanhoe Mines Ltd., the Canadian company that discovered the massive Oyu Tolgoi copper and gold deposit in the Gobi Desert.

There have been no accusations of improprieties by Ivanhoe, which is negotiating an agreement with the government on tax and other policies for developing the project.

Protesters said they were starting a hunger strike Tuesday that would add more people each day until opposition demands were met, said S. Ganbaatar, an activist with the Radical Reform, one of several civic groups claiming to represent the poor and unemployed.

They later marched to the headquarters of the Mongolian Revolutionary People's Party that leads the ruling coalition before returning to the central square and dispersing.

Protests have become increasingly common in Mongolia's 16-year-old democracy, with political parties often trying to capitalize on demonstrations and public disaffection. The current government, led by the Mongolian People's Revolutionary Party, was installed in January after a wave of demonstrations.

Copper mining is a major part of the economy of this impoverished former Soviet satellite, a sprawling grassland where many people are traditional nomadic herders of cattle and sheep.

Politicians have clashed repeatedly over how to exploit the country's mineral resources. The opposition accuses the government of giving away Mongolia's wealth and wants the national minerals law changed to give the government a large share in any foreign-owned mine.

Ivanhoe, based in Vancouver, British Columbia, has said its investment helps the Mongolian economy. The company said the project would generate 117,000 jobs and pay 46 percent of its pretax profits, or $7 billion, to the state over the contract's 35-year term.