Thailand has issued an emergency decree banning protests as it clamps down on largely peaceful pro-democracy rallies that have also targeted the monarchy.
The government said urgent measures were needed to “maintain peace and order”.
It justified the orders partly on the grounds of some protesters disturbing a royal motorcade during a mass march in Bangkok on Wednesday.
More than 20 people have been arrested including three protest leaders.
Thailand’s student-led democracy movement has been calling for the resignation of Prime Minister Prayuth Chan-ocha. The former army chief had seized power in a 2014 coup before he was appointed as premier after controversial elections last year.
The protests have widened in recent months to also call for curbs on the king’s powers.
The decree said protesters had intended to instigate an incident leading to “chaos and incitement of conflict and public disorder”.
Shortly after the decree took effect, Thai riot police cleared protesters from outside the prime minister’s office. Some tried to resist, using makeshift barricades, but they were moved back.
Hundreds of police were seen on the streets even after protesters were dispersed.
In addition to limiting gatherings to four people, the decree puts restrictions on the media, prohibiting the publication of news “that could create fear or intentionally distort information, creating misunderstanding that will affect national security or peace and order”.