Cambodian opposition leader Sam Rainsy has been stripped of his lawmaker status and parliamentary immunity, paving the way for his arrest in connection with a defamation case the opposition calls politically motivated.

Rainsy, who was in South Korea, has vowed to return to Cambodia as scheduled on Monday evening, three days after a court ordered his arrest.

The prospect of Rainsy's arrest has raised concerns of political demonstrations and violence.

The U.S. Embassy in Phnom Penh issued a security message warning of possible protests and urged citizens to immediately leave any area where there are large gatherings.

Rainsy's allies in the opposition party have accused Prime Minister Hun Sen of being behind the move to gain the upper hand in their ongoing political fight.