A woman carries a deck in front of a main Haitian police station, where according to local media a group of foreign nationals including Americans armed with semi-automatic weapons were detained, after anti-government protests, in Port-au-Prince, Haiti, February 18, 2019. REUTERS/Ivan Alvarado

(Reuters) - The serious crime unit of Haiti’s national police is investigating several foreign nationals, including Americans, who were arrested in possession of semi-automatic weapons, Prime Minister Jean-Henry Ceant said.

The group, which included five U.S. citizens, was arrested while driving in two vehicles on Sunday in the capital Port-au-Prince, adding to uncertainty in the impoverished Caribbean country after days of anti-government protests.

Ceant wrote on Twitter late on Monday that the investigation had been turned over to the Judicial Police Department, the detective service that works on serious organized and transnational crime in the poor Caribbean nation.

Ceant also said he had convened Haiti’s police security council, which includes the interior and justice ministers and senior police officials, to discuss the case. He did not say when the meeting would be held.

The U.S. State Department has said American citizens were part of the group but has not revealed their identities.

Names given by Haitian media correspond to social media profiles of American citizens and a Serbian who claim military backgrounds and currently work for security contractors.

National police chief Michel Ange Gedeon said the group face charges of illegal possession of weapons, Haitian newspaper Le Nouvelliste reported.

Thousands of Haitians have been staging demonstrations since Feb. 7, to demand the resignation of President Jovenel Moise amid allegations of corruption and over high inflation. The protests have receded in recent days.