Police in Myanmar have responded with increasing violence to protests against last week’s military coup, using water cannons, rubber bullets and live ammunition in a crackdown that left a woman in a critical condition on Tuesday. Tens of thousands of people marched in towns and cities across the country in defiance of a ban on gatherings in some areas to voice their opposition to the military takeover of the government. The police response the past three days had been mostly limited to using water cannons to disperse crowds, but escalated on Tuesday to include rubber bullets and live rounds mostly fired into the air as warning shots. Four people were taken to hospital in the capital Naypyidaw with what doctors initially said they believed were wounds caused by rubber bullets. One of them, a young woman, was struck in the head while wearing a motorcycle helmet and suddenly collapsed to the ground, video footage showed. The round was still lodged in her body and the wound was likely to be fatal, a doctor in the city told Reuters. “She hasn’t passed away yet, she’s in the emergency unit, but it’s 100% certain the injury is fatal,” said the doctor, who added that senior colleagues involved in her treatment had assigned him to speak to the media. “According to the X-ray, it’s a live bullet.” A man had a chest wound but was not in critical condition, the doctor said, and it was not clear if he was hit with a bullet or rubber bullet. Neither police nor the hospital responded to a request for comment. Earlier, officers had used water cannons to beat back the crowd, and demonstrators had responded by throwing projectiles. Footage on social media showed people running, with the sound of several gunshots in the distance. Opponents of the 1 February coup also gathered in Yangon and Mandalay, where evening curfews have been instituted and gatherings of more than five people are banned. Teargas was used against crowds in Mandalay, where police arrested at least 27 anti-coup demonstrators, including a journalist, media organisations said. A journalist from the Democratic Voice of Burma said he was detained after filming the rally and that people were beaten. Two media organisations confirmed the arrests. The United Nations expressed “strong concern” over reports of numerous people being injured. “The use of disproportionate force against demonstrators is unacceptable,” said Ola Almgren, the UN resident coordinator and humanitarian coordinator in Myanmar. The military takeover followed an election in November decisively won by Aung San Suu Kyi’s National League for Democracy that army leaders claim was fraudulent. The detention of Aung San Suu Kyi sparked outrage across the south-east Asian country of 53 million, and a growing civil disobedience movement affecting hospitals, schools and government offices. Demonstrations were also held on Tuesday in other cities, including Bago – where city elders negotiated with police to avoid a violent confrontation – and Dawei, and in northern Shan state. In Magwe in central Myanmar unconfirmed reports on social media claimed several police officers had crossed over to join the protesters’ ranks. Footage showed several officers running into a crowd being sprayed with water and using their shields to block the flow, as other officers tried to pull them back into formation. A video posted online from the delta city of Pathein appeared to show protesters persuading some police officers to stand down. “We know that you are human and have hearts that feel just like us,” one of the crowd of thousands could be heard telling officers at a barricade. An officer gestured that he could hear the demonstrators, drawing applause and loud cheers, and policemen started shaking hands with protesters and removing the barricade. The crowd marched past chanting, “The people’s police”. Outside Hledan Centre, a mall in Yangon, a crowd faced off against police barricades singing protests songs and chants despite the searing temperature. “We don’t care about the heat,” said a 24-year old protester who asked not to be named. “We want the police to join us. It is the army we are worried about. If they are told to shoot people, they will shoot.” Large crowds again gathered near Sule Pagoda in downtown Yangon, where one witness estimated there were tens of thousands on the streets by mid morning. Martial law and rumours of incoming soldiers had created an atmosphere of unease, but protesters were determined. Pyae Phyo, 33, was gathered with his friends from the Myanmar Seamen Union under the shade of a tree near Sule Pagoda. “Because of last night’s martial law announcement I thought people may not come,” he said. “But they have come. I am so proud of my people. Every day we will come here. Every day we aren’t free we will protest peacefully.” The protesters carried anti-coup placards including, “We want our leader”, in reference to Aung San Suu Kyi, and, “No dictatorship”. Pockets of ambulances manned by a network of volunteer doctors and medical workers were stationed near Sule Pagoda. Myat Moe Lwin, 25, a graduate doctor, and his colleague Kaung Pyae Sone Thin, 25, were waiting near the ambulances and were prepared to aid injured protesters. “So many people are protesting against the coup,” he said. “We had to help if there are any problems. It is our professional duty.” There was confusion over the reach of section 144 of the penal code, which bans gatherings of five or more people. The US embassy said it had received reports of an 8pm to 4am local time curfew in the two biggest cities, Yangon and Mandalay. Western governments have widely condemned the coup, although there has been little concrete action. The UN human rights council will hold a special session on Friday to discuss the crisis.