Elderly man punched repeatedly in robbery

An elderly man is in hospital after being repeatedly punched during a robbery in Sydney's south.

The 70-year-old was walking through Sylvania on Tuesday evening when two men riding pushbikes demanded money from him.

When he refused, one of the men punched him in the face several times, police say.

The man handed money over to the pair and drove himself to Sutherland Hospital.

He remains in a stable condition with swelling to his face and ear.

Police have appealed for information on the two men, who were described as Caucasian and aged between 25 and 30 years old.

One of the bikes was fitted with a small motor.