Thailand's military rulers say they are monitoring a new form of silent resistance to the coup - a three-fingered salute borrowed from The Hunger Games - and will arrest those in large groups who ignore warnings to lower their arms.

The raised arm salute has become a symbol of opposition to Thailand's May 22 coup, and a creative response to bans on political gatherings of more than five people.

Junta spokesman Colonel Weerachon Sukhondhapatipak said that authorities were "monitoring the movement" and would take action if the salute is performed in large groups.

He said that if protesters ignore a warning to stop, "we will have to make an arrest".

In The Hunger Games books and films, the salute symbolises rebellion against totalitarian rule.