ULAN BATOR, Mongolia — Police fired rubber bullets and tear gas to disperse angry protesters who mobbed the headquarters of the ruling political party Tuesday, alleging fraud in a weekend election that centered on how to share the country's mineral wealth.

Thousands of protesters threw rocks at riot police outside the offices of the Mongolian People's Revolutionary Party, parts of which were on fire. Some protesters set a car ablaze.

Police responded with rocks, rubber bullets, tear gas and water cannons, but the protesters showed no signs of disbanding. Some had bloody faces after apparently being struck.

"The demonstrators are acting like hooligans and violating social order," said police spokesman Sainbayar, who like some Mongolians goes by one name.

Other protesters pushed into the General Election Commission offices to demand that they resign over voting irregularities and fraud. Complaints center on two districts in Ulan Bator which protesters say were wrongly awarded to the MPRP.

According to preliminary results, the MPRP — which also governed the country when it was a Soviet satellite — won 46 seats in Sunday's vote. That would give the party far more than half of the 76 seats in parliament, called the State Great Khural.

The other major party, the Mongolian Democratic Party, took 26 seats. An independent won one seat and a minor party another. Results in two other seats were not yet clear. The General Election Commission has until July 10 to announce the final results.

Tuesday's clashes far surpass the usual minor violence that has often accompanied elections in the 18 years since Mongolia cast off communist rule for democracy.

Police seemed unprepared to deal with the mostly young crowd, who trampled one police officer, apparently leaving him badly injured.

Prime Minister Bayar Sanjaa blamed Elbegdorj, head of the Mongolian Democratic Party, for inciting the violence.

"Elbegdorj made the very irresponsible statement of denouncing election results while official results were not yet announced," he said.

The General Election Commission has defended the vote and said it was working within the proper legal framework. But at least one party has called for a re-count in some districts of Ulan Bator.

"The Mongolian people voted for democracy and not for the MPRP, who are ex-communists," said Magnai Otgonjargal, vice chairman of the Civic Movement Party.

Mongolia, a mostly poor country sandwiched between China and Russia, is struggling to modernize its nomadic, agriculture-based economy. The government says per capita income is just $1,500 a year.

The two main political parties focused their campaigns on how to tap recently discovered huge mineral deposits — including copper, gold and coal — but disagreed over whether the government or private sector should hold a majority stake.

The difference meant the outgoing parliament was unable to pass an amendment to the Minerals Law, which kept the government from concluding investment agreements with international mining giants to develop mineral deposits in the Gobi Desert.

With a large majority, the MPRP may now be able to have parliament pass the new law.

The current Minerals Law gives the government the right to take up to a 50 percent interest in an important mineral deposit if state funds were used to discover it.

The proposed change would give Mongolia a minimum 51 percent stake. But while the MPRP wants the government to hold that stake, the Mongolian Democratic Party says private Mongolian companies should be able to hold it.

Parliamentary elections are held every four years. Mongolia, which is slightly smaller than the U.S. state of Alaska with a population of nearly 3 million, stopped being a satellite state of the Soviet Union in 1990.