Mischa Gaillard, the opposition coalition spokesman, said: "We don't want confrontation. The police have not done their duty to serve and protect. Since our strategy is a peaceful one, we have cancelled the demonstration."

Mr Aristide's regime has been rocked in the past week by a series of armed insurrections which have seen rebels capture a dozen or so towns.

The president's supporters, armed with baseball bats and wearing balaclavas, said they were protecting democracy.

"They don't want elections. They want to take over. We are here to protect the police because they are in a minority," said Amos Giffrard, 50. "Democracy hangs in the balance."

"The opposition came to take over the police station. We came to stop these terrorists," said Bernabe Mervil, 33.

The political situation remained volatile across the country yesterday, with the government and the opposition preaching peace, but increasingly dependent on violent gangs to strengthen their bargaining position.

The government has regained control of three towns, but with no army and only 4,000 police, Mr Aristide's grip on power remains precarious.

Yesterday's events will place the president under increasing international pressure to resolve the crisis peacefully, following growing criticism of human rights abuses to crush dissent.

"We are extremely concerned about the wave of violence spreading through Haiti," Scott McClellan, President George Bush's press secretary, said.

The death toll rose to 49 after three anti-government rebels were executed by Aristide supporters in St Marc, a town the government recaptured on Monday.

Meanwhile, in the country's second city, Cap Haitien, Aristide supporters also erected blazing barricades to block a feared rebel incursion.

Mr Aristide has branded attempts to remove him as a coup d'etat. "I will leave the palace on February 7 2006," he said in his first news conference since the uprising began.

Yesterday the US secretary of state, Colin Powell, said that Canada and Caribbean countries may send police reinforcements to back the Haitian government. "The policy of the administration is not regime change. President Aristide is the elected president of Haiti," he said.

The Port-au-Prince opposition, a coalition of human rights campaigners, students and business people, is demanding Mr Aristide's immediate resignation and a two-year transitional government to replace him. But it has distanced itself from the armed uprisings.

Mr Aristide still retains considerable support among Haitians, particularly among the poorest of the country.