The unarmed PCs were investigating a burglary in Knatchbull Road, Camberwell, when they came under fire around midday on Monday.
The officers were not injured in the incident.
A statement by Metropolitan police said searches to trace the suspect were ‘ongoing’ and the force’s Trident Gang Command was helping with the investigation.
The suspect who is thought to have fired at officers is described as black, aged in his 20′s, wearing a blue puffa-style jacket and blue jeans.
He was with another man who was white, aged in his 20′s and wearing a parker-style coat.
Knatchbull Road remains closed.
Anyone who has information or sees the two suspects is asked to call 999 immediately. Alternatively they can ring Crimestoppers anonymously on 0800 555 111.