Entire Washingon DC National Guard called in

Tensions spiked outside the White House on Sunday, the scene of three days of demonstrations amid unrest across America against police killings of black people.

The entire Washington, DC National Guard - roughly 1,700 soldiers - was called in to help control the protests, according to two Defense Department officials who insisted on anonymity because they were not authorized to publicly discuss the matter.

Police fired tear gas and stun grenades into a crowd of more than 1,000 chanting protesters across the street from the White House in Lafayette Park.

The crowd ran away and piled up road signs and plastic barriers to light a raging fire in a nearby street.

Some pulled an American flag from a building and threw it into the blaze.