A surfer was last night in a serious condition after being attacked by a shark off Streaky Bay in South Australia.

Police say the 48-year-old man was surfing at Back Beach when he was bitten on the arm.

The man was in the water with a group of friends and his daughter when the shark struck, the Seven network reported.

The surfer, who is in a serious condition, was taken to Streaky Bay hospital before being transferred to Royal Adelaide Hospital, it reported.