EXCLUSIVE

Justin Bieber was in a car accident in Bev Hills Tuesday at 2 PM PDT ... after a car driven by a paparazzo was chasing the Escalade in which Bieber was a passenger -- eyewitnesses tell TMZ.

We're told the Escalade was going down Canon Drive at a fast clip, trying to lose the photog, when a BMW was pulling out of a parking structure near Bouchon restaurant. An eyewitness tells us ... the BMW misjudged the speed of the Escalade and smashed into it.

We're told Bieber almost immediately got out of the SUV and into another car and sped off.