WH on lockdown as protests over black man death reach Washington

The White House has been put under a lockdown as protests over the death of an unarmed black man in custody, reached Washington on the fourth day of nationwide demonstrations against the incident in Minneapolis.

Online video showed hundreds of protesters in Lafayette Park just outside the White House on Friday, chanting "No justice, no peace", reports Xinhua news agency.

One protester sprayed the Freedman's Bank Building, while some other demonstrators clashed with Secret Service personnel, witnesses said.

The doors to the White House briefing room have also been locked and Secret Service officers were not letting anyone off White House grounds, local media reported.

"Secret Service personnel are currently assisting other law enforcement agencies during a demonstration in Lafayette Park. In the interest of public safety we encourage all to remain peaceful," the Secret Service tweeted.

George Floyd, aged 46, died on Monday evening shortly after Derek Chauvin, a white police officer, held him down with a knee on his neck although the victim repeatedly pleaded, "I can't breathe", and "please, I can't breathe".

On Friday, Chauvin was arrested and charged with three-degree murder and manslaughter.

Floyd's family and their lawyer, Benjamin Crump, said in a statement to NBC News that the arrest was "welcome but overdue".

The family said they wanted a more serious, first-degree murder charge as well as the arrest of the other officers involved.

"The pain that the black community feels over this murder and what it reflects about the treatment of black people in America is raw and is spilling out onto streets across America."

Minneapolis Mayor Jacob Frey on Friday imposed a mandatory night-time curfew following three straight nights of growing protests and violence in the biggest city in the state of Minnesota.

The city has been severely damaged in the protests and riots, with fires burning and businesses looted.

The police precinct closest to where Floyd was captured on video was set on fire late Thursday night.

The state's Governor Tim Walz on Thursday declared a state of emergency and activated the Minnesota National Guard to restore order.

Potests over Floyd's death continued on Friday night in Minneapolis and a number of other cities, including New York, Los Angeles, Chicago, Denver, Phoenix and Memphis, local media reported, adding that more demonstrations were expected to take place across the country through the weekend.