BANGKOK — Thai riot police cleared thousands of protesters from outside the Thai Prime Minister's office early on Thursday (Oct 15) as an emergency decree banned large gatherings and the publication of sensitive news in the face of escalating protests.

A series of demonstrations over three months have brought tens of thousands of people onto the streets of Bangkok to demand the departure of Thai Prime Minister Prayuth Chan-ocha, a former junta leader, and a new constitution.

They have also broken a longstanding taboo by calling for reforms to the powerful monarchy of Thailand's King Maha Vajiralongkorn — and in an act cited by the Thai government as one reason for its emergency measures they obstructed a royal motorcade.

Shortly after the emergency decree took affect at 4am (5am SGT), riot police advanced behind shields on protesters who had camped outside Government House. Many of the thousands who had protested there late on Wednesday had already left.

Some protesters tried to resist with makeshift barricades of garbage cans, but they were swiftly pushed back. By dawn, hundreds of police occupied the nearby streets and city workers began cleaning up.

At least three of the protest leaders were arrested, Thai Lawyers for Human Rights said. Police made no immediate comment.

The Thai government said it acted in the face of increasing disorder and after the obstruction of the motorcade.

"It is extremely necessary to introduce an urgent measure to end this situation effectively and promptly to maintain peace and order," state television announced.

The emergency decree bans big gatherings of five or more people and allows authorities to stop people from entering any area they designate.

It also prohibits "publication of news, other media, and electronic information that contains messages that could create fear or intentionally distort information, creating misunderstanding that will affect national security or peace and order."

Thai Lawyers for Human Rights said that three protest leaders had been arrested. It named them as Parit Chirawat, rights lawyer Arnon Nampa and Panupong Jadnok.

It said Arnon had been arrested on charges related to a speech he gave in the northern city of Chiang Mai. It said it did not know the grounds for the other arrests.

Tens of thousands of protesters marched in Bangkok on Wednesday.

The protest movement aims to remove Prayuth, who took power in a 2014 coup that was meant to end a decade of violence between supporters and opponents of the country's establishment.

Those marching on the streets also want a new constitution and have called for a reduction in the powers of the Thai king.

Protesters shouted at the Thai king's motorcade in Bangkok on Tuesday after the arrest of 21 protesters. On Wednesday, some protesters slowed a convoy carrying Queen Suthida, giving the three-finger salute and chanted "get out" at police protecting the vehicle. REUTERS