Troops have joined police in forcefully dispersing marchers in the city of Mandalay in northern Myanmar, as protests against the military coup continued despite the deployment of extra soldiers in some areas and an eight-hour internet blackout overnight. Images and reports from the city on Monday showed police and soldiers using rubber bullets and slingshots to disperse protesters. A student union in the city said several people had been injured. In the capital, Naypyidaw, protesters gathered outside a police station demanding the release of a group of high school students who were detained while joining in anti-coup activities. One student who managed to escape told reporters that the pupils – thought to range in age from 13 to 16 – were demonstrating peacefully when a line of riot police arrived and began arresting them. It was not clear exactly how many students were rounded up, but estimates put the figure at between 20 and 40. Myanmar resurfaced online at about 9am local time on Monday after an internet-monitoring service showed a dramatic fall in connectivity from midnight. There were fears the blackout might be used as cover for mass arrests or violence. “Before 1am we were still checking up on each other, calling to confirm that we were each in a safe place,” said a protest organiser who came from a family of activists. “Anything could have happened last night based on my experience living under the military regime and dealing with the military intelligence and special branch. I have been worried since day one of the coup. I haven’t slept well since day one.” There was no sign of overnight violence on Monday, but the country woke to extra troops on the streets of many cities including the former capital Yangon, where the new forces on the ground included the 77th light-infantry division which, during pro-democracy protests in 2007, was accused of ramming demonstrators and using live ammunition against them. Protests continued in the city despite the show of force, albeit in numbers smaller than the peaks of Friday and the weekend. Students and Buddhist monks demonstrated in front of the troops, and a banner reading “We do not want military government” was stuck to an army vehicle outside Yangon’s central bank. “Patrolling with armoured vehicles means they are threatening people,” said 46-year-old Nyein Moe, among the more than 1,000 gathered in front of the central bank in Yangon. “People are marching on the streets and they don’t care to be arrested or shot. We can’t stop now. The fear in our mind is going away.” There was a new rally in the southern city of Dawei, too, a verified livestream on Facebook showed, with hundreds of protesters accompanied by a marching band. Crowds also gathered outside the headquarters of the National League for Democracy, the civilian party that won November’s general election but whose top leaders, including Aung San Suu Kyi, were detained when the military took power on 1 February. Aung San Suu Kyi’s detention on charges of illegally importing six walkie-talkie radios was due to expire on Monday but her lawyer said she would be remanded in detention until Wednesday for a court hearing. Aung San Suu Kyi had spoken to a judge via video conferencing, her legal team said, and she had asked if she could hire a lawyer. Speaking in Naypyidaw on Monday morning, Khin Maung Zaw said he was still trying to see his client in line with the law. When asked about the fairness of the proceedings, the lawyer said: “Whether it is fair or not, you can decide yourself.” Since the coup, hundreds of thousands of people have taken to the streets to call for an end to Aung San Suu Kyi ’s detention in the nation’s biggest protests in more than a decade. The unrest has revived memories of bloody outbreaks of opposition to almost half a century of direct army rule, which ended when the military began a process of withdrawing from civilian politics in 2011. On Sunday, police opened fire to disperse protesters at a power plant in northern Myanmar, but violence in this month’s protests has been limited. As well as the demonstrations around the country, the military rulers are facing a strike by government workers, part of a civil disobedience movement that is crippling many of the functions of government. Soldiers were deployed to power plants in the northern state of Kachin, leading to a confrontation with demonstrators, some saying they believed the army intended to cut off the electricity. The security forces fired to disperse protesters outside one plant in the state capital, Myitkyina, footage broadcast live on Facebook showed, although it was not clear if they were using rubber bullets or live fire. On Sunday evening, armoured vehicles appeared in the commercial capital of Yangon, Myitkyina and Sittwe, the capital of Rakhine state, the first large-scale rollout of such vehicles across the country since the coup. The government and army could not be reached for comment. Shortly after midnight, residents reported an internet outage. All four telecommunications networks were inaccessible from about 1am until 9am on Monday, when connections were restored. Monitoring group NetBlocks reported that a “state-ordered information blackout” had taken Myanmar almost entirely offline, but services began resuming around the start of the working day. In the early days after the coup, the internet was cut across the country. The army has been carrying out nightly arrests and on Saturday gave itself sweeping powers to detain people and search private property. On Sunday, it published penal code amendments aimed at stifling dissent. “It’s as if the generals have declared war on the people,” UN special rapporteur Tom Andrews said on Twitter. “Late night raids; mounting arrests; more rights stripped away; another Internet shutdown; military convoys entering communities. These are signs of desperation. Attention generals: You WILL be held accountable.” The amendments to the penal code set out a 20-year prison term for inciting hatred of the government or military or hindering the security forces engaged in preserving state stability. Hindering the security forces carrying out their duties is punishable by seven years in prison while spreading fear, fake news or agitating against government employees gets three, according to the amendments posted on a military website. In the latest sign of disruption by workers, the government’s civil aviation department said in a statement many staff had stopped coming to work since 8 February, causing delays to international flights. A pilot, who asked not to be identified for fear of retribution, said hundreds of staff from the department were striking. Some trains also stopped running after staff refused to go to work, domestic media reported.