Gonaives, Haiti ? Haitian rebels seeking to topple the president brought in reinforcements from the neighboring Dominican Republic, including the exiled former leader of 1980s death squads and a former police chief accused of fomenting a coup, witnesses said Saturday, as police fled two more northern towns.

Twenty commandos arrived, led by Louis-Jodel Chamblain, a former Haitian soldier who headed army death squads in 1987 and a militia known as the Front for the Advancement and Progress of Haiti, or FRAPH, which killed and maimed scores of people in the early 1990s.

Guy Philippe, a former police chief who fled to the Dominican Republic after being accused by the Haitian government of fomenting a coup in 2002, also arrived in Gonaives to help the rebels prepare for an expected showdown with the government. It was unclear when the volunteers arrived.

Witnesses reached by telephone said the men were working with rebels in Gonaives but were massing in Saint-Michel de l’Atalaye, 28 miles to the east.

The rebels launched a bloody uprising nine days ago from Gonaives, 70 miles northwest of Port-au-Prince and Haiti’s fourth-largest city, seeking President Jean-Bertrand Aristide’s ouster. About 50 people have been killed.

“Chamblain and his men are taking advantage of the situation to further their own ends, ends that would mean the perversion of the democratic movement,” said Himler Rebu, an opposition leader and former army colonel who led a failed coup attempt in 1989 against Lt. Gen. Prosper Avril.

He warned the international community that the longer Aristide stays in power, the harder it will be to restore order in Haiti.

Secretary of State Colin Powell said Friday the United States and other nations would “accept no outcome that … attempts to remove the elected president of Haiti.”