Yangon , Myanmar ( CNN ) -- Buddhist monks and others armed with swords and machetes Friday stalked the streets of a city in central Myanmar , where sectarian violence that has left about 20 people dead has begun to spread to other areas , according to local officials . Members of the Buddhist and Muslim communities in Meiktila township have clashed this week after a dispute between a Muslim gold shop owner and two Buddhist sellers Wednesday ignited simmering communal tensions . Rioters have set fire to houses , schools and mosques , prompting thousands of residents to flee their homes amid unrest that had echoes of sectarian troubles that killed scores of people in western Myanmar last year . Late Friday night , President Thein Sein announced on state television that four townships in the affected region are under a state of emergency . The United Nations and the United States have expressed concern about the violence in the lakeside city about 100 kilometers ( 60 miles ) south of Mandalay . Win Htein , an opposition member of parliament for Meiktila , said the number of dead in the city has risen to about 20 by his estimate -- most of them Muslims -- after charred bodies were found in the streets . `` I have not seen this scale of violence before in my life , '' he said . `` I am very sad . The community used to live in peace . '' Myanmar is emerging from decades of military repression and has taken a number of significant steps toward democracy in recent years under President Thein Sein . But it has been plagued by bouts of ethnic violence that some analysts say are a byproduct of the changing political climate . Burning mosques . A group of about 100 Buddhists , including some monks , went around Meiktila on Thursday night torching mosques , said Police Lt. Col. Aung Min , and while most of them have returned home , some are still wandering the streets , carrying weapons . Although Aung Min declined to provide an official death toll , he said the violence had spread to a nearby town , Win Twin , where a mosque was burned down overnight . He said about 1,000 Muslims had taken temporary shelter in a soccer stadium in Meiktila , where about 30 % of the 100,000 residents are estimated to be Muslims . Win Htein said he believed that more than 5,000 Buddhists had fled to monasteries around the city to escape the violence . Many members of both communities had lost their homes , he said . Journalists in the city who tried to take photos of the clashes said they were threatened by Buddhists , some of them monks , who were holding sticks and knives . Violence in Rakhine . In the western state of Rakhine , tensions between the majority Buddhist community and the Rohingya , a stateless ethnic Muslim group , boiled over into clashes that killed scores of people and left tens of thousands of others living in makeshift camps last year . Most of the victims were Rohingya . `` The ongoing intercommunal strife in Rakhine State is of grave concern , '' the International Crisis Group said in a November report . `` And there is the potential for similar violence elsewhere , as nationalism and ethno-nationalism rise and old prejudices resurface . '' A failure by authorities to address deepening divisions between the communities could result in a resumption of violence in the future , the report said , `` which would be to the detriment of both communities , and of the country as a whole . '' Vijay Nambiar , special adviser to the U.N. secretary-general on Myanmar , on Thursday expressed `` deep sorrow at the tragic loss of lives and destruction '' in Meiktila this week . He called for `` firm action '' from Myanmar authorities , combined with `` the continued fostering of communal harmony and preservation of peace and tranquility among the people . '' Win Htein , the local lawmaker , said that he believed there were now about 1,000 police officers in the area . He said he had spoken to Aung San Suu Kyi , the Nobel laureate and leader of the opposition National League for Democracy , who had said local authorities should use police to control the situation according to the law . The U.S. ambassador to Myanmar , Derek Mitchell , said Thursday that he was `` deeply concerned '' about the reports of violence . Journalist Phyo Wai Lin reported from Yangon , CNN 's Kocha Olarn reported from Bangkok , Thailand , and CNN 's Jethro Mullen reported and wrote from Hong Kong .
Four townships in central Myanmar under a state of emergency , the president says . The rioting has driven thousands of people from their homes , officials say . Clashes started with a dispute between a Muslim shop owner and Buddhist sellers . Last year , ethnic violence in western Myanmar left scores of people dead .