The authorization was based on "heightened potential for violence, continued telecommunications restrictions, and limited flights out of Burma", according to a statement from the U.S. Embassy in Burma.
Groups of demonstrators turned out early in Yangon and other cities to protest the February 1 coup and demand that the nation's elected leader, Aung San Suu Kyi, and members of her ousted government be freed from detention.
"Patrolling with armoured vehicles means they are threatening people", said 46-year-old Nyein Moe, among the more than 1,000 gathered Monday in front of the Central Bank, staring down armoured vehicles parked there.
However, Suu Kyi has not been seen for two weeks.
"We don't want to live under a military dictatorship". "Now everything is settled". Her lawyer, Khin Maung Zaw, could not be reached for comment on what was set to happen. Large demonstrations have been held across the country every day since February 6.
NetBlocks, which tracks Internet disruption, said on its Twitter account that connectivity was being restored as of Monday morning, but that social media was shut down for eight hours from 1:00 a.m.
The shutdown comes after a day of protesters taking to the streets in defiance of heavy troop presence around Yangon - although turnout was smaller than in recent days.
The United Nations denounced the choking of the internet.
Youths held placards reading "Free Aung San Suu Kyi" and "We support CDM", the latter referring to the civil disobedience movement.
Armoured vehicles were deployed on Sunday in Yangon, the northern town of Myitkyina and Sittwe in the west, the first large-scale use of such vehicles since the coup.
Myanmar security forces opened fire yesterday to disperse protesters in the city of Mandalay, the media outlet Frontier Myanmar reported.
Demonstrators retaliated by throwing bricks, said a rescue team member who assisted with the injured.
Demonstrators retaliated by throwing bricks, according to a medic at the scene, while journalists said police had beaten them in the melee.
Monitoring group NetBlocks reported that a "state-ordered information blackout" had taken Myanmar nearly entirely offline early Monday.
"It's a big worry and concern for the villagers".
More than 384 people have been detained since the coup, the monitoring group Assistance Association for Political Prisoners said, in a wave of mostly nightly arrests.
Foreign embassies in Myanmar, including those of the US and European Union member states, issued a joint statement Sunday saying they "unequivocally condemn the detention of political leaders, social activists and civil servants" and called for an end to violence against protesters.
By late Monday night, the United Kingdom embassy in Myanmar took a harsher line, admonishing the regime for its attack on journalists and for imposing another internet blackout.
"The assault on freedom of expression must stop", it tweeted.
The military has justified the coup as a response to alleged massive irregularities in last November's general election that saw Suu Kyi's NLD win another resounding victory against a military-backed opposition party. This is theater. It's just theater.
The self-styled Committee Representing the Pyidaungsu Hluttaw has 15 members who met online and said they have enough support to convene Parliament.
"In a kind of an ironic way, the generals have proven their capacity to unify the country in ways that I have never seen", he added. They accuse Beijing of propping up the military regime and applaud Washington's actions sanctioning the military.