|In Chicago, fires destroyed at least 20 buildings.
|1968: United States erupts in race violence
Dozens of major cities in the United States have been rocked by an escalation in the race riots which began two days ago.
At least 19 people have died so far in the arson, looting and shootings provoked by the assassination of black civil rights leader Martin Luther King on 4 April.
Several hundred have also been injured and about 3,000 people have been arrested - most of those in Washington DC.
Curfews are in place in many areas of the country and National Guard soldiers have been mobilised to help quell the violence which is threatening to engulf the US in a race war.
Twelve thousand troops in the nation's capital were called on to help protect fire fighters tackling at least eight blazes started by rioters.
Other fires started in Chicago were accompanied by looting and sniping, and at least 20 buildings have been completely destroyed.
There have also been 38 arson attacks in Detroit, shootings reported in Pittsburgh and a four-hour gun battle at Tennessee State University.
For every Martin Luther King who falls, 10 white racists will go down with him
United Black Front chairman Lincoln Lynch
Dr King's immediate successor, Reverend Ralph Abernathy, has repeatedly appealed for calm.
The new head of the Southern Christian Leadership Conference of Atlanta has appeared on television urging people to respect the murdered leader's commitment to non-violent protest.
But United Black Front chairman Lincoln Lynch said black Americans should adopt a new stance.
"It isimperativeto abandon the unconditional non-violent concept expounded by Dr King and adopt the position that for every Martin Luther King who falls, 10 white racists will go down with him.
"There is no other way - America understands no other language," he said.
A national day of mourning in the US for Dr King will take place on 7 April.