Ulan Bator - Mongolian President Nambariin Enkhbayar declared a four-day state of emergency Wednesday amid violent riots in the capital Ulan Bator, that killed two and injured up to 100, according to authorities.

Twenty demonstrators were arrested during the protests alleging fraud in the weekend's parliamentary elections, which focused on how to share the country's mineral wealth, and saw the opposition fare worse than expected.

Protesters ransacked and set fire to the headquarters of the ruling Mongolian People's Revolutionary Party (MPRP) on Tuesday, and later damaged another official building, parts of the cultural palace and an art gallery, witnesses reported.

A curfew from 10 pm to 8 am allowed special forces to bring the situation under control, officials said.

Witnesses said police used teargas to disperse the mostly youthful demonstrators. Some 25 people were injured in the clashes, described by analysts as the worst in two decades, among them a Japanese journalist, police and protesters.

Tsakhia Elbegdorj, the chairman of the opposition Democratic Party (DP), had earlier accused the MPRP of election manipulation, saying the results were dishonest.

Elbegdorj claimed there were cases of vote-buying and bribing of election observers. He did not provide any concrete proof, but pointed to the great disparity between pre-election opinion polls and the actual results for his party.

According to latest results the MPRP won 46 of the 76 seats in the State Great Khural, or parliament, after being in a dead heat with the rival Democratic Party going into Sunday's elections.

Unconfirmed reports put the Democratic Party's showing at just 26 seats. The Election Commission said final results were expected to be available Wednesday.

About 74 per cent of 1.5 million registered voters cast their ballots Sunday, well below pre-poll estimates.

How to handle the rights to recently discovered mineral deposits - including copper, gold and coal - were the basis of the campaigns for the two political parties.

With a large majority, the ruling party will be able to pass the current Minerals Law which gives the government the right to take an interest of as much as 51 per cent in an important mineral deposit if state funds were used to discover it.

The Mongolian Democratic Party says private Mongolian companies should be able to hold the majority stake. (dpa)