PORT-AU-PRINCE, Haiti, March 3 ? Gun battles broke out today between rebels and supporters of the deposed president, Jean-Bertrand Aristide, as Haiti continued to grapple with the violence and lawlessness that has overrun the country in the last month.

United States marines guarding the National Palace did not interfere with nearby gun battles, in which police allied with rebel soldiers exchanged fire with Aristide supporters.

But the marines have intervened on the road to the airport, to keep rebels from interfering with convoys of Aristide backers who were trying to leave the country.

The rebel leader, Guy Philippe, said at a news conference today that his group was prepared to turn their weapons over to the interim president, Boniface Alexandre. But Mr. Alexandre, who is chief justice of the Supreme Court, has not been seen in public since a news conference on Sunday when he announced he would take office.

The new president’s authority was uncertain, too. The constitution says his appointment requires ratification by the Legislature, which was dissolved in January. The constitution also provides for presidential authority to be held by a council led by the prime minister.

On Tuesday, Mr. Philippe proclaimed “The country is in my hands,” as he met hundreds of supporters near the palace that last held Mr. Aristide, the constitutionally elected president. Mr. Aristide left Haiti early Sunday for the Central African Republic after a shove from the United States.

In the absence of any other authority, Haiti seemed to be falling into the clutches of a self-appointed armed junta. Despite the rebels’ vow to restore order, violence continued in the capital on Tuesday. Six bodies of people killed by gunshot wounds were brought to the morgue, bringing the total stored there from violence over the past week to about 25.

Although American officials denounced the armed rebels and said they should have no role in ruling Haiti, the Americans did not take steps to confront them.

Col. David H. Berger, the Marine Corps commander here, said his troops would not act as police officers. “I have no instructions to disarm the rebels,” he said.

The contingent of marines dispatched to Haiti by President Bush grew to 450 Tuesday, officials said. They stuck mostly to the airport and the National Palace. Several guarded Prime Minister Yvon Neptune’s residence. About 100 French and Canadian troops have also arrived.

The rebels’ power grab was met with silence or muted support by members of the political opposition to the Aristide government; inaction from United Nations diplomats, who have promised to form a multinational peacekeeping force for Haiti; and contempt from Washington, where officials dismissed Mr. Philippe as a nonentity.

“He is not in control of anything but a ragtag band,” an assistant secretary of state, Roger Noriega, told the Senate Foreign Relations Committee.

But no one else appeared to be in charge. The armed rebels reigned in Port-au-Prince, having seized government installations on Monday, and vowed to resurrect the army.

Mr. Neptune, the prime minister, whom Mr. Philippe threatened to arrest, met Tuesday with the American ambassador, James B. Foley, the White House said.

Mr. Philippe paraded through the streets like a conqueror. His men scoured the slums, which formed Mr. Aristide’s strongest political base, seeking out Aristide loyalists.

The rebels sought to fill the vacuum left by Mr. Aristide’s fall, and were moving faster than what remains of the government of Haiti.

“It is an absolutely failed state ? no institutions, no rule of law, no spirit of compromise, no security,” said Robert Pastor, director of the Center for Democracy and Election Management at American University. Mr. Pastor has monitored elections here since 1987.

Complicating the political chaos, Jean-Claude Duvalier, Haiti’s former “president for life,” said in Miami that he planned to return to Haiti, where he maintains a small group of nostalgic supporters.

His rule began when his father, François, the dictator known as Papa Doc, died in 1971, and it ended when the army overthrew him in 1986. During the three-decade Duvalier dynasty, the government killed thousands of opponents and stole many millions from Haiti’s treasury.

The Haitian Army, which earned a reputation for brutality and corruption, overthrew Mr. Aristide in 1991. He returned, backed by American force, in 1994, and dissolved the army in 1995.