The pair were battling for sixth place in the closing stages of the Albert Park race, with Russell closing in on Alonso, having pitted later and with the benefit of fresher tyres.
Approaching Turn 6, Russell appeared to suddenly gain on the Aston Martin ahead, which destabilised his Mercedes and sent him over the gravel and into a heavy hit with the wall.
Russell has confirmed he is OK having been checked over the by FIA medical team and after the race the incident was placed under investigation by the stewards.
Speaking to Sky Sports F1, Russell held back on accusing Alonso of wrongdoing but felt the scenario was "bizarre".
"My take is that I have gone off, and that is on me, but I was half a second behind Fernando 100m before the corner and then suddenly he came towards me extremely quick and I was right in his gearbox," Russell said.
"I don't know if he has got a problem or not. We are off to see the stewards so that is a bit bizarre in a circumstance like this. I've got nothing more to say right now, I need to see everything, I am disappointed to end the race like that."
When asked directly if he felt Alonso brake-tested him, Russell replied: "It is clear that he braked 100m before the corner and then went back on the throttle again and took the corner normally.
Source: Autosport