Numerous protesters were arrested for defying a curfew in Baltimore Friday night, hours after six police were charged over the death of an African-American man who was in their custody.

The protesters struck a defiant chord with police, even after the six officers were charged earlier in the day over the death of 25-year-old Freddie Gray.

The scene contrasted with Thursday night, when protesters largely cleared the street as the 10 pm curfew set in.

The curfew was imposed following mass protests and riots earlier in the week in the city about an hour's drive north of Washington.

"Officers are arresting protesters who refused to leave after the curfew went into effect," the Baltimore Police Department said on Twitter.

READ: Police enforce curfew in riot-hit Baltimore

One of the protesters told CNN he felt he was "being arrested unjustly. This is my city. These police don't live here, I do."

Thousands of demonstrators had hit the street earlier in the day, despite the charges against the six officers.

The charges ranged from second-degree murder and manslaughter to misconduct and were announced in a surprise statement by Maryland state prosecutor Marilyn Mosby.

All six officers -- three of them black and three white, according to mugshots broadcast by CNN -- were taken into custody and later posted bond, reports said.

The death of Gray, 25, who is the latest African American to lose his life at the hands of police, has reignited simmering resentment in the United States over law enforcement tactics, particularly in their dealings with African Americans.

"The findings of our comprehensive, thorough and independent investigation, coupled with the medical examiner's determination that Mr Gray's death was a homicide... have led us to believe that we have probable cause to file criminal charges," Mosby said.

Mosby said Gray "suffered a severe and critical neck injury as a result of being handcuffed, shackled by his feet and unrestrained" inside a moving police van following his arrest on April 12.

PHOTO ALBUM: Unrest in Baltimore

Cheers broke out when Mosby unveiled the charges on the steps of Baltimore's war memorial, across the street from City Hall, a focal point of protests demanding justice and change.

Baltimore's police union condemned what it called "an egregious rush to judgment" as it defended the officers and expressed confidence they would be vindicated.

"We believe that these officers will be vindicated as they have done nothing wrong," said Michael Davey, a lawyer for the city's Fraternal Order of Police, suggesting that prosecutors had succumbed to pressure from days of demonstrations.


More protests


But if authorities had hoped the announcement would ease tensions on the streets, the daytime march and night protests proved them wrong.

Several thousand people rallied from City Hall through downtown streets lined with riot police, demanding justice and an end to alleged racism and police brutality.

As they walked past a phalanx of officers, many chanted: "Send those killer cops to jail, the whole damned system is guilty as hell."

Brian Carter, a nurse, 39, told AFP: "I was overwhelmed with joy, I'm not going to lie. The Baltimore police, they're not all bad, but they are very prejudiced towards people."

Smaller demonstrations have also took place in recent days in New York, Philadelphia, Washington and Boston, and hundreds again congregated in Union Square, in the center of Manhattan, as police helicopters buzzed overhead.


Shock


William Murphy, a lawyer for the Gray family, told reporters they had no advance word of the charges.

"We were in shock -- and it was a good shock, do you know what I mean?" he said, while Gray's step-father Richard Shipley appealed for peace to prevail in the city.

Gray, who had a record of non-violent drug offenses, died a week after his arrest from spinal injuries sustained when he was arrested in a west Baltimore public housing project.

Facing the most serious charge, second-degree murder, is African American officer Caesar Goodson, the driver of the van that transported Gray to a police station.

Goodson, 45, was also charged with involuntary manslaughter, second-degree assault, vehicular manslaughter and misconduct.

Goodson got out of the van to check on Gray's condition, Mosby said, but "at no point did he seek nor did he render any medical assistance."

Three other officers were charged with involuntary manslaughter, second-degree assault and misconduct, and two more charged with second-degree assault and misconduct.

One officer was also charged with false imprisonment.

Mosby -- an African-American woman who is the daughter, granddaughter and niece of police officers -- said Gray had been "illegally arrested" as "no crime had been committed."

In an open letter, Baltimore's police union called for a "special independent prosecutor" to take over the case from Mosby, who at 34 is America's youngest big-city chief prosecutor.


Conflicts of interest?


The letter cited Mosby's relationships with Murphy, who contributed $5,000 to her election campaign, and her husband, a city council member who represents the poverty-stricken section of Baltimore where Gray lived and died.

Baltimore police lieutenant Kenneth Butler added: "We are extremely frustrated and shocked by the circumstances that have transpired today."

Gray has become the latest face of an intense national debate over whether American police are too quick to use violence against unarmed black males.

In the best-known recent case, a white police officer fatally shot unarmed teenager Michael Brown in Ferguson, Missouri -- prompting riots in the St Louis suburb -- and protests around the country. The officer was not indicted by a grand jury.