Benton Harbor, a poor and predominantly black town on the shore of Lake Michigan, was also under curfew after two nights of fire and rage following the death of a black man in a high-speed chase by white police officers.

About 250 state troopers used tear gas and batons early yesterday to quell rioting in which fire trucks and ambulances were stoned and shot at, and passing motorists were dragged from cars and beaten. The troopers were ready for further violence last night. "It looks like a war zone. It's terrible," Dorothy King, who lives near the crash site, told a local paper. "I'm scared to go to bed."

Terrance Shurn, 28, died late on Sunday night in a chase that ended when he lost control of his Honda motorcyle and crashed into a derelict house at 100mph.

His last previous brush with the law was in February, when he was arrested and charged with possession of a single Vicodin painkiller pill.

The impact of his death was instantaneous on a town that has suffered a steady economic decline, which has long chafed at police harassment, and where there is reason to fear high speed chases by police - in the streets where Shurn crashed, at least two others had died over the last two years, one being an 11-year-old boy struck and killed on the pavement.

Within 24 hours, mourners had placed blue and gold balloons over the skid marks at the crash site. When police moved in to break up a vigil, protesters set an abandoned house on fire, and threw bricks and bottles at squad cars. Outnumbered, the police withdrew. Protesters' rage was amplified by a story circulating that Shurn was knocked over by a squad car. However, Samuel Harris, the local police chief, said the car was following him a few blocks behind.

On Tuesday night, 48 hours after the first eruption, the authorities admitted they had lost control over the town of 12,000, and called out the state riot police. Flames ripped through five residential buildings as protesters shot at and stoned firetrucks and the occasional ambulance. Passing motorists were dragged out of their cars. At least 10 people were injured. "It's a real mess," a Michigan state police dispatcher told reporters at the scene. "We have a riot. We're in a state of emergency. There are buildings on fire. There have been gunshots. The crowd has pulled civilians out of cars and beat them."

The immediate outcome has been a promise by the town police to review their policy of permitting high speed chases.

Shurn, and another motorcyclist, had at first been tailed by other police on a highway outside town, and the chase had been abandoned because the two were travelling at more than 100mph. When they entered Benton Harbor proper, the local police resumed the chase.

The declaration of a state of emergency allows Michigan's governor, Jennifer Granholm, to call in additional forces such as the National Guard. However, a statement from her urged local people to work with police in the town to restore calm.

"The civil unrest of recent days must come to an end, and the healing process must begin for the future of the community," it said. "We will provide assistance both in ending the violence and enabling the healing process in Benton Harbor."

Although once a tourist destination, the town has been part of the greater midwestern industrial decline, and its boat yards and factories have shut down.

People claim that they are discriminated against by police who come from neighbouring, mainly white communities, which are better off.

"The real underlying cause, in my opinion, is that we have a segregated community up here," Charlie Ammeson, a local lawyer, told reporters. "The fear, the distrust, that develops just gets blown out of proportion."

The strength of feeling in Benton Harbor has indeed taken officials by surprise.

"It is so unnecessary. It is unbelievable to see this in our community," said Mr Harris.

"We had gunfire. They shot at our trucks, they shot at the captain of police, ran barricades."