Teachers and students in Myanmar have rallied to a growing civil disobedience campaign as the anti-coup protest movement won the support of ousted leader Aung San Suu Kyi's party.
Stepping up measures to quell discontent, police arrested one of Ms Suu Kyi's veteran aides and dozens of people who had joined noisy demonstrations against Monday's coup.
International pressure on the junta increased with the UN Security Council urging the release of detainees and Washington considering sanctions on the ruling generals.
Teachers became the latest group to join a civil disobedience campaign with some lecturers refusing to work or cooperate with authorities over the coup that halted a long and unsteady transition to democracy.
"We want the military coup to fail," lecturer Nwe Thazin Hlaing said at the Yangon University of Education.
The disobedience campaign, which began with doctors, has also spread to some government offices and on Friday won the formal backing of Ms Suu Kyi's National League for Democracy party.
In a statement, the party denounced the coup and Ms Suu Kyi's detention as "unacceptable" and said it would help people who are arrested or sacked for opposing the takeover.
Army chief Min Aung Hlaing took power citing alleged irregularities in a November election that the party won in a landslide.
The electoral commission has said the vote was fair.
There has been no outpouring of people onto the streets in a country with a bloody history of crackdowns on protests but there were signs of coup opponents growing bolder - with dozens of youths parading in the southeastern city of Dawei.
Teachers and students of Myanmar Mercantile Marine College flash three-finger salutes as they protest against the military coup in Yangon Source: EPA
In the biggest city, Yangon, supporters hung red clothing, ribbons and balloons outside their homes to show support.
"We put red balloons down the whole street," said Myint Myint Aye, 49.
"This is a non-violent campaign. We want to show the dictators that all of us are with Mother Suu."
But authorities also began to step up action against coup opponents.
In Myanmar's second city of Mandalay, 30 people were arrested over pot-banging protests which have taken place for the last three nights.
Eleven Media quoted Maung Maung Aye, deputy head of the regional police force, as saying they were accused of breaking a law against "causing noise in public streets".
The latest high-profile detainee was 79-year-old Win Htein, a stalwart of Ms Suu Kyi who was repeatedly imprisoned during their decades of struggling against previous juntas.
"I have never been scared of them because I have done nothing wrong my entire life," he told Reuters by phone as he was taken away.
Reuters was unable to reach police for comment on his arrest or what charges could be brought against him.
The 15-member UN Security Council released a statement on Thursday calling for the release of all detainees and for respect for human rights, fundamental freedoms and the rule of law.
Meanwhile, Norwegian telecom Telenor says mobile operators and internet service providers have been ordered to block access to Twitter and Instagram in the country until further notice.
The government had already ordered internet providers on Thursday to block Facebook, which counts half of the population of 54 million as users, until 7 February.
The Ministry of Communications and Information Technology did not immediately answer a request for comment but said previously it had blocked Facebook for the sake of "stability".
A spokeswoman for Twitter, which is also facing pressure from authorities in India, said it was "deeply concerned".
