Mongolian President Nambariin Enkhbayar has declared a state of emergency for four days, after Mongolians alleging election fraud clashed with police and set fire to the headquarters of the ruling party.
At least five people were killed and more than 300 injured in the rioting in Mongolia's capital Ulan Bator.
Some 700 people were detained for their part in the violence.
The chaos threatens to further delay deals that could unlock vast reserves of coal, uranium and other resources beneath the country's vast steppes and deserts, and are seen as key to lifting the isolated Central Asian state out of poverty.
The state of emergency means protests are banned and authorises security forces to break up protests using force. Central areas have been put under curfew and alcohol sales are banned over the period.
Riot police fired tear gas against protesters last night, but struggled to bring under control crowds, who threw stones, burned cars and gathered in their thousands in the main square of Ulan Bator to protest against alleged election fraud.
Rioting continued into this morning. Witnesses reported hearing gunfire. Conditions calmed after convoys of police and armoured vehicles arrived to disperse rioters, witnesses said.
The blaze at the party headquarters had been extinguished, and state television showed MPRP Prime Minister Sanjaagiin Bayar touring the charred building and folding his hands in prayer. An uneasy calm enveloped the city this morning with a heavy police presence guarding government buildings.
Mongolia's election committee has yet to give the final result of Sunday's vote, but preliminary results give the ruling Mongolian People's Revolutionary Party (MPRP) a clear majority in the 76-seat parliament.
The leader of the opposition Democratic Party Tsakhiagiin Elbegdorj rejected the results, but international observers say that overall the election was free and fair.
The Democratic Party had called its candidates from around the country to Ulan Bator, where they intended to present details of election fraud.
The country of vast grasslands and deserts is often viewed as a rare example of democracy in Central Asia. But new election rules that changed the first-past-the-post system to one of multi-member constituencies have led to procedural problems and some confusion over how votes should be counted.