Baltimore was a city on edge Tuesday as hundreds of National Guardsmen patrolled the streets against unrest for the first time since 1968, hoping to prevent another outbreak of rioting.

Maryland's governor said 2,000 Guardsmen and 1,000 law officers would be in place overnight to try to head off a repeat of the racially charged violence set off Monday by the case of Freddie Gray, a 25-year-old black man who died of a spinal-cord injury under mysterious circumstances while in police custody.

It was the worst such violence in the U.S. since the unrest that erupted last year over the death of Michael Brown, the unarmed black 18-year-old shot by a white police officer in Ferguson, Missouri.

"This combined force will not tolerate violence or looting," Gov. Larry Hogan warned.

In a measure of how tense things were, Baltimore was under a citywide 10 p.m.-to-5 a.m. emergency curfew.

All public schools were closed. And the Baltimore Orioles cancelled Tuesday night's game at Camden Yards and -- in what may be a first in baseball's 145-year history -- announced that Wednesday's game will be closed to the public.

The streets were largely calm all day and into the evening, with only a few scattered arrests. The real test was expected after dark.

As the 10 p.m. curfew went into effect, several hundred protesters remained in the street in the city's Penn North section near where a pharmacy was looted. Standing shoulder to shoulder, police in helmets and riot shields began advancing toward the demonstrators in an effort to push them back. Some protesters lay in the street or hurled bottles toward the police.

As the hour drew near, a local pastor used a loudspeaker to urge the demonstrators to go home, saying: "Let's show the world, because the eyes of the world are on Baltimore right now."

 

 

Around the same time and in a different neighbourhood, Baltimore police tweeted that they were making arrests in South Baltimore after people started attacking officers with rocks and bricks. At least one officer was reported injured.

Monday's looting, arson and rock- and bottle-throwing by mostly black rioters broke out just hours after Gray's funeral

Political leaders and residents called the violence a tragedy for the city and lamented the damage done by the rioters to their own neighbourhoods.

"I had officers come up to me and say, 'I was born and raised in this city. This makes me cry,"' Baltimore Police Commissioner Anthony Batts said.

Haywood McMorris, manager of the wrecked drug store, said the destruction didn't make sense: "We work here, man. This is where we stand, and this is where people actually make a living."

But the rioting also brought out a sense of civic pride and responsibility in many Baltimore residents, with hundreds of volunteers turning out to sweep the streets of glass and other debris with brooms and trash bags donated by hardware stores.

The crisis marks the first time the National Guard has been called out to deal with unrest in Baltimore since 1968, when some of the same neighbourhoods that rose up this week burned for days after the assassination of the Rev. Martin Luther King Jr. At least six people died then, and some neighbourhoods still bear the scars.

At the White House, President Barack Obama called the deaths of several black men around the country at the hands of police "a slow-rolling crisis." But he added that there was "no excuse" for the violence in Baltimore, and said the rioters should be treated as criminals.

"They aren't protesting. They aren't making a statement. They're stealing," Obama said.

The rioting started in West Baltimore on Monday afternoon and by midnight had spread to East Baltimore and neighbourhoods close to downtown and near the baseball stadium.

At least 20 officers were hurt, one person was critically injured in a fire, more than 200 adults and 34 juveniles were arrested, and nearly 150 cars were burned, police said. The governor had no immediate estimate of the damage.

The violence set off soul-searching among community leaders and others, with some suggesting the uprising was about more than race or the police department -- it was about high unemployment, high crime, poor housing, broken-down schools and lack of opportunity in Baltimore's inner-city neighbourhoods.

The city of 622,000 is 63 per cent black. The mayor, state's attorney, police chief and City Council president are black, as is 48 per cent of the police force.

In the aftermath of the riots, state and local authorities found themselves facing questions about whether they let things spin out of control.

Batts, the police commissioner, said police did not move in faster because those involved in the early stages were just "kids" -- teenagers who had just been let out of school.

Mayor Stephanie Rawlings-Blake waited hours to ask the governor to declare a state of emergency, and the governor hinted she should have come to him earlier.

"We were trying to get in touch with the mayor for quite some time," Hogan said. "She finally made that call, and we immediately took action."

Rawlings-Blake said officials initially thought they had the unrest under control.

Grey was arrested April 12 after running away at the sight of police, authorities said. He was held down, handcuffed and loaded into a police van. Leg cuffs were put on him when he became irate inside. He died a week later.

Authorities said they are still investigating how and when he suffered the spinal injury -- during the arrest or while he was in the van, where authorities say he was riding without being belted in, a violation of department policy.

Six officers have been suspended with pay in the meantime.