An explosion at a petrol station in Sydney’s southwest has left two men injured, one with serious burns.

More than 50 firefighters are battling the blaze at a Metro service station in Belmore after being confronted by a large fire and collapsing walls on arrival.

Emergency services arrived at the scene about 3pm on Saturday, with NSW Police closing roads in the area.

The two injured men were hospitalised, with one suffering serious burns.

Police said firefighters had contained the blaze at the Canterbury Road petrol station but it was continuing to burn.

Footage on social media showed thick black smoke rising into the air visible from blocks away, while video from firefighters showed the blaze in a building away from the petrol bowsers.

One Twitter user described seeing people jumping out of windows at the scene of the blaze.

Police said inquiries into the fire were continuing, with anyone with information urged to contact Crime Stoppers.