A crowd estimated at 300 people gathered in Tottenham, north London, to demand justice for the man's death, Sky News reported.
The BBC reported Metropolitan Police said riot officers were deployed after the protesters threw projectiles at the squad cars, setting them ablaze. The officers also had bottles and other objects thrown at them, police said.
The British network said the demonstration was held in response to Thursday's shooting death of Mark Duggan, a 29-year-old father of four.
"... A number of bottles were thrown at these two cars -- one was set alight and the second was pushed into the middle of the High Road. It was subsequently set slight," the BBC quoted an unidentified police spokesman as saying.
"The officers were not in the vehicles and were unhurt."
One member of the crowd, Vanessa Robinson, said the protest started peacefully, but turned into "absolute chaos."
Maria Robinson of Tottenham called the situation "absolutely manic" and said people were throwing bottles, "making bottle bombs," setting fires and breaking into shops.
David Akinsanya, 46, who also lives in the neighborhood, said several shop windows had been smashed.
"It's really bad," he said. "There are two police cars on fire. I'm feeling unsafe. It looks like it's going to get very tasty. I saw a guy getting attacked."