Gunmen fired Sunday on thousands of protesters demanding the prosecution of Jean-Bertrand Aristide (search), drawing return fire from U.S. Marines and leaving five people dead in the worst attack since the Haitian president's ouster.

Demonstrators scattered as shots crackled across the vast Champs de Mars plaza (searchin front of the presidential National Palace. Police ducked into doorways. One fired off a string of shots from a submachine gun; another threw a wounded colleague over his shoulders and hauled him to safety, still pointing his pistol down the street.

Blood slicked the floor of an operating room at a private hospital where wounded lay waiting for treatment. Women screamed and men cried as the few doctors short of drugs struggled to treat the wounded. Most of the victims were in serious condition with wounds from assault rifles, said surgeon Ronald Georges (search).

The shooting marked the first known instance of U.S. Marines opening fire since they were sent to stabilize Haiti a week ago, but angry survivors accused the Marines and their French colleagues of not doing enough to prevent the attack.

Several witnesses said they saw Aristide militants open fire from the roof of the Rex movie theater across the plaza as thousands of people gathered in front of the National Palace. U.S. military spokesman Maj. Richard Crusan said it was unclear who the gunmen were.

He told The Associated Press that three Marines on the grounds of the palace returned fire, shooting in the direction of the theater. No Marines were wounded.

Ricardo Ortega, a New York correspondent for the Spanish television station Antena 3, was shot in the chest and abdomen and died at the hospital.

Among more than 30 injured people was Fort Lauderdale Sun-Sentinel photographer Michael Laughlin, 37, who was shot in the face and shoulder but was in stable condition at the hospital.

As doctors struggled to treat the wounded, a French military helicopter made a dramatic landing on the traffic-clogged road in front of the Canape Vert Hospital. Two men descended to wheel a gurney of emergency medical supplies.

The protesters had been calling for Aristide to stand trial on charges of corruption and the alleged murders of opponents killed by his armed militants.

Aristide fled Haiti Feb. 29 as fighters from a popular rebellion were reaching Port-au-Prince, the capital, and the United States and France were urging him to step down.

Some witnesses said gunmen first appeared Sunday outside the old Defense Ministry building on the plaza, then kneeled on the sidewalk and opened fire.

Others said gunmen in two all-terrain vehicles started the shooting, while others said they saw gunmen shooting down from the roof of the Rex movie theater at the other end of the plaza from the palace.

Crusan said three Marines on the grounds of the palace — not sharpshooters on the roof — "heard reports that there was shooting coming from the direction of the theater and we believe that we responded to that."

Some protesters complained the foreign forces had not provided enough security.

"The peacekeepers were nowhere near where the shooting was," said Almil Costel, 31, who was shot twice in the left shoulder.

French commander Col. Daniel Leplatois defended the peacekeepers. "We're not able to secure the lives of all of the demonstrators," he said.

After the shooting, a truck with loudspeakers drove around the palace, blaring music. One man speaking over its loudspeaker shouted at the U.S. Marines: "People are dying every day in this country. You have to do something about it."

Aristide supporters had planned a separate demonstration Sunday but said they were offered no protection by the peacekeepers and were afraid of attacks from anti-Aristide activists. Their protest was rescheduled for Monday, although leaders said they still were worried about security.

"The Americans are only here to protect those who helped oust Aristide," said Ednar Ducoste, 23, an Aristide supporter. "If we had guns, we would be fighting against them right now."

On Sunday, Aristide released a statement through government officials in the Central African Republic, where he is in exile, saying he was "well looked-after" and would personally address reporters at an unspecified time. Aristide has said the United States forced him from power at gunpoint, something U.S. officials deny.

Earlier, during Sunday's march in Port-au-Prince, demonstrators tore down a billboard featuring Aristide's face. Rebel leader Guy Philippe was hoisted onto supporters' shoulders as they chanted "Guy Philippe — hero! Aristide — zero!"

Philippe, a former Aristide police chief accused of coup-plotting, reiterated Sunday that he had no political aspirations.

There were also cheers for Louis-Jodel Chamblain, an ex-soldier convicted in the killings of Aristide supporters. Like movie stars, both Chamblain and Philippe were surrounded by autograph-seekers.

Rebels have refused to give up their weapons, despite Philippe's pledge to disarm. Marines have faced shouted insults from armed Aristide militants furious over their leader's ouster and what they call "an occupation army."

A recently appointed seven-member "Council of Sages" met for a third day Sunday in the capital to choose a new prime minister. Officials said they hoped to have a decision by Tuesday.

Prime Minister Yvon Neptune, an appointee and confidante of Aristide whom Sunday's protesters also said should be tried, condemned the violence and defended the Marines return of fire, saying they abided by "rules of engagement (that) permit that they use proportional force."

Among those being considered to replace Neptune is Lt. Gen. Herard Abraham, probably the only Haitian army officer to voluntarily surrender power to a civilian. Abraham succeeded ousted Gen. Prosper Avril in 1990 and immediately handed power to Haiti's Supreme Court justice. That laid the way for the transition to 1990 elections that Aristide won in a landslide.

Another choice is Smarck Michel, a businessman who was Aristide's prime minister in 1994-1995 but resigned over differences in economic policy.