Britain and Canada later imposed sanctions on Myanmar generals for human rights violations following the military takeover that provoked widespread outrage.
Hackers have attacked Myanmar government websites to protest against the military coup, as the junta pressed on with its attempts to stymie nationwide opposition with internet blockades and troop deployments.
The cyber attacks came a day after tens of thousands of people rallied across the country to protest against the generals toppling Aung San Suu Kyi's civilian government earlier this month.
A group called Myanmar Hackers disrupted websites including the Central Bank, the Myanmar military's propaganda page, state-run broadcaster MRTV, the Port Authority, and the Food and Drug Administration.
"We are fighting for justice in Myanmar," the group said on its Facebook page.
"It is like mass protesting of people in front of government websites."
Cybersecurity expert Matt Warren from Australia's RMIT University said it was likely the aim was to generate publicity.
"The sorts of attacks they would be undertaking are denial of service attacks or defacing websites which is called hacktivism," he told AFP.
"The impact will be potentially limited but what they are doing is raising awareness."
Internet access was severely curtailed for the fourth night, according to NetBlocks, a Britain-based group that monitors internet outages around the world.
It said connectivity had dropped to just 21 percent of ordinary levels, and was restored eight hours later ahead of the start of the working day.
"The practice is detrimental to public safety and incites confusion, fear and distress in difficult times," NetBlocks tweeted.
UK, Canada places sanctions on officials
The UK foreign ministry said it was imposing sanctions on three junta officials, including the ministers of defence and home affairs, and had begun a review to stop UK businesses working with the regime.
"The UK condemns the military coup and the arbitrary detention of Aung San Suu Kyi and other political figures," Foreign Secretary Dominic Raab said in a statement.
"We, alongside our international allies, will hold the Myanmar military to account for their violations of human rights and pursue justice for the Myanmar people," he added.
Canadian Foreign Minister Marc Garneau announced a broader sanctions list affecting nine officials in Myanmar.
"The sanctions announced today are part of a united response to send a clear message that Canada will not accept the actions of the Myanmar military and their complete disregard for t he will and democratic rights of the people of Myanmar," he said.
Three-quarters of the country’s civil servants are on strike, all private banks are closed and the protests have weakened the economy significantly, said Tom Andrews, the independent UN human rights expert on Myanmar.
For a second day, some motorists in Yangon blockaded roads with vehicles, leaving their bonnets up and pretending they were broken down to stop security forces from moving around Myanmar's biggest city.
Many motorists drove at a snail's pace in a show of opposition to the coup.
Buses and cars could be seen on live feeds parked around a bridge at North Dagon on Thursday morning, as protesters chanted: "Don't attend the office, leave it. Join the civil disobedience movement."
"We need the US Army to save our situation," read a sign held by a monk in saffron robes.
Dozens of police patrolled the vicinity of Myaynigone junction as motorists also blocked roads.
"We gathered about five taxies and one pretended his car had broken down and blocked the street. Others also surrounded him. But we didn't stay long. We blocked (for) about 30 minutes," said a 30-year-old taxi driver.
"We are doing this to cause difficulties for police. If they come and it's a little bit tense, we leave then."
Than Than, a street food vendor, said the traffic snarls were a minor inconvenience, but she supported the campaign.
"I walked about 40 minutes because of cars blocking my way back home yesterday afternoon before I got a bus," the 50-year-old told AFP.
State railway workers continued to strike on Thursday despite a police rampage the previous night targeting them in a sign of the military junta’s concern over growing civil disobedience by public workers protesting the coup.
The police rampage in a Mandalay neighbourhood where state railway workers are housed showed the conflict between protesters and the new military government is increasingly focused on the businesses and government institutions that sustain the economy
State railway workers on Sunday had called a strike, joining a loosely organised Civil Disobedience Movement that was initiated by medical workers and is the backbone of the resistance to the February 1 coup that ousted the elected civilian government.
The railway strike has received support from ordinary citizens who have placed themselves on railroad tracks to stop trains the military has commandeered.
The efforts by Mandalay residents to block a rail line on Wednesday apparently triggered the retaliation that night.
Less than an hour after the 8 pm (1330GMT) start of the nightly curfew, gunshots were heard as more than two dozen men in police uniforms, shields and helmets, marched in tight formation by the railway workers’ housing.
Numerous videos posted on social media showed muzzle flashes as shots were heard, and some were shown shooting slingshots and throwing rocks at buildings. Cadence calls of “left, right, left, right” can be heard along with shouts of “shoot, shoot.”
Several reports included photos of people with small wounds, which were claimed to have been caused by rubber bullets.
Four train drivers participating in the civil disobedience movement were arrested at gunpoint, then taken to a Mandalay locomotive factory and forced to drive to the northern city of Myitkyina, the Assistance Association for Political Prisoners said.
The group has reported that close to 500 people have been arrested since the coup.
In a further sign of the military's efforts to stifle the protest movement, state broadcaster MRTV said arrest warrants had been issued for several popular actors, directors and a singer.
They are accused of using their "popularity and fame" to encourage people to join the civil disobedience movement, MRTV said.
March 1 hearing for Suu Kyi
The military has justified its power grab alleging widespread voter fraud in November elections won by Suu Kyi's National League for Democracy party in a landslide.
Western powers and the United Nations have repeatedly condemned the coup.
After her detention in a dawn raid on February 1, Suu Kyi was charged with possessing unregistered walkie-talkies.
This week Suu Kyi has been hit with a second criminal charge related to holding an election campaign event last year which the junta claims breached coronavirus restrictions.
Her lawyer Khin Maung Zaw has not been able to meet with his client and is worried about the confidentiality of discussions if he is only allowed to speak to her by phone or video call ahead of a March 1 hearing.