National police spokesman Gary Desrosiers said the Americans were jailed because they were acting as if they were part of Haiti's military on Friday during a demonstration to demand that President Michel Martelly restore the country's armed forces, which was abolished in 1995 because of its abusive record
The march by hundreds of former soldiers and their young recruits in Haiti's capital turned violent and 50 participants were detained.
On Saturday, authorities said Americans Zeke Petrie, 39, of Barberton, Ohio; and Steven Shaw, 57, of Massachusetts, were among those in jail. Police say they were driving vehicles with pro-army demonstrators in the march when they were picked up a few blocks from the National Palace.
Petrie wore a black T-shirt with the army's name on it and Shaw wore camouflage pants.
"I'm friends with the guys," Petrie told The Associated Press from behind bars at the Canape Vert police station. "These guys are working for the betterment of the country."
Petrie, an occasional interpreter for foreign journalists, said he hadn't been formally charged but overheard police say he would be charged with "working with terrorists."
Two other Americans, Benjamin Depp, 29, a freelance photojournalist from Waxhaw, North Carolina, and John Strutner, 22, a volunteer at Child Hope International from Monterey, California, along with Canadian Seanna McLeod, 38, a volunteer at a malnutrition clinic from Courtenay, British Columbia, were held overnight in the lobby of the police station after trying to bring insulin, syringes and swabs to Petrie, who says he's diabetic.
Desrosiers said he knew nothing about the three people held overnight, but each of them told the AP that government prosecutor Jean-Renel Senatus said they had to stay at the police station until they answered questions with an attorney and an interpreter about how they knew Petrie.
Senatus didn't return repeated calls on Saturday.
Later Saturday, Haitian police shut down two of the 10 old military bases the former soldiers had been occupying and the wannabe soldiers fled to an undisclosed location.
Secretary of State for Public Security Reginald Delva said the rest of the bases would soon be closed.
"The move is on," said Delva. "That's two down, and we're moving on to the other ones."
The paramilitary-like presence of the former soldiers, and their regular marches and occupations in mismatched uniforms, had become an embarrassment to the U.N. peacekeeping mission and the Haitian government, which hopes to court foreign investors.
Friday's rally began peacefully but some people near the National Palace threw rocks amid a heavy U.N. presence. A few of the men in military uniforms carried handguns. That evening, police exchanged gunfire outside an old army base in the Carrefour district outside Port-au-Prince.
Four civilians were treated for gunshot wounds Friday night at two Doctors Without Borders clinics in Carrefour, said Mathieu Fortoul, a spokesman for the international health charity.
It was not immediately clear if they were shot in the gunfire surrounding the demonstration, Fortoul said.
Martelly has said he wants to revive the military but that it must be done legally. Under pressure from the U.N., his administration has repeatedly called for the lightly armed men to drop their weapons and clear out of the bases they've taken over since February. But until Friday and Saturday the government had taken little action to disband the group of men.