Rainham Road South has been cordoned off since the morning today (August 26) after police were called to the scene at 8.53am.
A man, 41, was treated at the scene before he was taken to hospital.
His condition is assessed as life-threatening, the Metropolitan Police said.
Two men were arrested shortly after the incident.
This includes a 38-year-old arrested on suspicion of grievous bodily harm, robbery and failing to provide a breath test.
A 48-year-old was also arrested on suspicion of grievous bodily harm and robbery. Both men remain in custody.
They both remain in custody.
Anyone with information is asked to call police on 101 quoting reference CAD 2236/26August.
