A confrontation between the Thai authorities and anti-government demonstrators that has escalated in recent days jumped to an uncertain new phase on Friday, as protesters were forcibly dispersed and two of the movement’s participants were charged with violating an obscure law against endangering the royal family.

Riot police officers deployed powerful water cannons for the first time, drenching demonstrators with a stinging liquid and carrying out a spate of new arrests in a crackdown that has hit the protests with an arsenal of threats, diktats and detentions.

The invoking of the arcane law, which carries up to life imprisonment for committing "an act of violence against the queen’s liberty,” added to the tensions in Thailand, which has been periodically engulfed by political turmoil and is known for strict measures to prevent disparaging the king and his kin.