The United Nations condemned a violent crackdown in Myanmar on Sunday and urged the country's military rulers to stop using force on peaceful demonstrators

"We strongly condemn the escalating violence against protests in Myanmar and call on the military to immediately halt the use of force against peaceful protesters," Ravina Shamdasani, spokeswoman for the UN human rights office, said in a statement.

Myanmar has been in chaos since the army seized power and detained elected government leader Aung San Suu Kyi and much of her party leadership on February 1, alleging fraud in a November election her party won in a landslide.

The coup, which brought a halt to tentative steps towards democracy after nearly 50 years of military rule, has drawn hundreds of thousands onto the streets and the condemnation of Western countries.

On Sunday, the police fired on protesters in the bloodiest day of weeks of demonstrations against a military coup and over ten people were killed and several wounded. The UN human rights office and Reuters said at least 18 people were dead.

Police were out in force early and opened fire in different parts of the biggest city of Yangon after stun grenades, tear gas and shots in the air failed to break up crowds. Soldiers also reinforced police.

Several wounded people were hauled away by fellow protesters, leaving bloody smears on pavements, media images showed. One man died after being brought to a hospital with a bullet in the chest, said a doctor who asked not to be identified.

Police also opened fire in Dawei in the south, killing three and wounding several, politician Kyaw Min Htike told Reuters from the town.

The dead in Yangon included a teacher, Tin New Yee, who died after police swooped to disperse a teachers' protest with stun grenades, sending the crowd fleeing, her daughter and a fellow teacher said.

Police also hurled stun grenades outside a Yangon medical school, sending doctors and students in white lab coats scattering. A group called the Whitecoat Alliance of medics said more than 50 medical staff had been arrested.

Police broke up protests in other towns, including Lashio in the northeast, Myeik in the deep south and Hpa-An in the east, residents and media said.

Nevertheless, at least 14 protesters have now died in the turmoil. The army said a policeman has been killed.

The crackdown would appear to indicate determination by the military to impose its authority in the face of defiance, not just on the streets but more broadly in the civil service, municipal administration, the judiciary, the education and health sectors and the media.

While Western countries have condemned the coup and some have imposed limited sanctions, the generals have traditionally shrugged off diplomatic pressure. They have promised to hold a new election but not set a date.

Suu Kyi's party and supporters said the result of the November vote must be respected.

Suu Kyi, 75, who spent nearly 15 years under house arrest, faces charges of illegally importing six walkie-talkie radios and of violating a natural disaster law by breaching coronavirus protocols. The next hearing in her case is on Monday.

A UN official said the office had confirmed at least five people dead in Yangon. Police Sunday also opened fire in Dawei in the south, killing three and wounding several.

The Myanmar Now media outlet reported two people had been killed in a protest in the second city of Mandalay. Security forces fired again later in the day and one woman was killed.