BANGKOK (AP) — Thailand’s government declared a strict new state of emergency for the capital on Thursday, a day after a student-led protest against the country’s traditional establishment saw an extraordinary moment in which demonstrators heckled a royal motorcade.

After the pre-dawn declaration, riot police moved in to clear out demonstrators who after a day of rallies and confrontation had gathered outside Prime Minister Prayuth Chan-ocha’s office to push their demands, which include the former general’s stepping down, constitutional changes and reform of the monarchy.

Several top leaders of the protest movement were taken into custody, with one later declaring on his Facebook page that he had been denied access to a lawyer and was being forced onto a helicopter and taken to a city in the country’s north. Police said they had made 22 arrests.

Despite a new ban against large public gatherings, several thousand people answered calls to rally again in another area of the city later Thursday.

The text of the emergency declaration said it was needed because “certain groups of perpetrators intended to instigate an untoward incident and movement in the Bangkok area by way of various methods and via different channels, including causing obstruction to the royal motorcade.”

The protest Wednesday in Bangkok’s historic district, not far from glittering temples and royal palaces, was the third major gathering by student-led activists who have been pushing the boundaries of what is considered acceptable — and legal — language by publicly questioning the role of Thailand’s monarchy in the nation’s power structure.

Thailand’s royal family has long been considered sacrosanct and a pillar of Thai identity. King Maha Vajiralongkorn and other key member of the royal family are protected by a lese majeste law that has regularly been used to silence critics who risk up to 15 years in prison if deemed to have insulted the institution.

The protest — held on the anniversary of a 1973 student-led uprising against a military dictatorship — was complicated by the presence of royalist counter protesters who had gathered both to show support for the government and to greet the royal family as they traveled to and from a religious ceremony in the area.

That led to a moment captured in photos and video that circulated widely on social media in which what appeared to be protesters gestured and shouted just meters (feet) from the royal motorcade. Such actions are unprecedented in Thailand, where those waiting for a royal motorcade regularly sit on the ground or prostrate themselves.

Some experts say a line may have been crossed.