Myanmar's military has warned anti-coup protesters across the country that they could face up to 20 years in prison if they obstruct the armed forces.
Long sentences and fines will also apply to those found to incite "hatred or contempt" towards the coup leaders, the military said.
The legal changes were announced as armoured vehicles appeared on the streets of several cities.
Hundreds of thousands of people have taken part in protests in recent days.
The demonstrators are demanding the release from detention of their elected leaders, including Aung San Suu Kyi, and the restoration of democracy.
On Monday, Ms Suu Kyi's lawyer said she would be detained for a further two days. She will then be tried via video link at a court in the capital Nay Pyi Taw on Wednesday, Khin Maung Zaw added.
Ms Suu Kyi was rounded up with other members of the government on 1 February, but her detention was due to end on 15 February, according to Reuters news agency.
The charges against her include possession of unlawful communication devices - walkie-talkies used by her security staff.
Her party was elected in a resounding victory last November, but the military has alleged voter fraud without providing proof.