Thailand imposed “serious” emergency measures banning gatherings of more than four people in a bid to stop youth-led demonstrations that have been rocking the country since mid-July.

The protesters have called for Premier Prayut Chan-Ocha to step down, while some prominent activists have demanded reforms to the kingdom’s unassailable monarchy.

“Free our friends!” they chanted as they blocked off a major Bangkok intersection, watched on by hundreds of riot police.

Many held up a three-finger salute which has been harnessed as a symbol of the burgeoning movement.

The gathering comes the day after a tense anti-government rally saw thousands gather to call for reforms to the monarchy.

After the emergency measures were announced, police moved to disperse protesters — who stayed through the night outside Government House — and arrested 22 activists.

The emergency decree gives authorities powers to arrest protesters without warrants, and also to seize “electronic communications equipment, data and weapons” suspected to be linked to the move.

Online messages that “threaten national security” are also banned.