Cambodia has deployed troops and held live firing drills in preparation for the possible return of an opposition leader who is an arch-rival of the country's strongman premier.
Sam Rainsy, who has lived in France since 2015 to avoid jail for convictions he says are politically motivated, has promised a dramatic return on November 9, Cambodia's Independence Day.
But Prime Minister Hun Sen has warned Rainsy will be arrested on sight and police have rounded up dozens of opposition activists in advance.
Defence Minister Tea Banh told reporters Monday night that troops are in place at the Thai-Cambodian border.
"We consider this a coup attempt," Tea Banh said.
Firing exercises with live rounds were held in border provinces, a government spokesman told AFP Tuesday.
But Rainsy doubled down on the homecoming in a video released on Tuesday, and called for Cambodians to be "united to remove the traitor Hun Sen".
Observers are not convinced Rainsy will attempt the return without Hun Sen's sign-off, as he has done in the past.
Hun Sen, who has ruled for 34 years, has widened his grip on power after an election last year in which his ruling party swept all seats.
The poll, widely derided as a sham, was held after Cambodia's Supreme Court dissolved the opposition Cambodia National Rescue Party and arrested one of its co-founders.