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, state television said on Wednesday.
"The president has declared a state of emergency according to the constitution ... from 11:30 pm on July 1 for a period of four days," television said.
Riot police fired tear gas against protesters on Tuesday night, but struggled to bring under control crowds, who had gathered in their thousands on the main square in the heart of the capital Ulan Bator to protest preliminary results.
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 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.