A SIX-year-old girl has saved her younger brother from a would-be kidnapper in Victoria's southeast by running to his aid.

The four-year-old boy was playing in the family driveway on Townsend St, Port Welshpool, in South Gippsland, at 9pm on Wednesday night when a man in his 50s tried to drag him away.

His sister saw the attempted kidnapping before running to her brother's aid by ordering the attacker to let the boy go.

The pair then ran inside before the would-be child abductor fled.

He was described as Caucasian, with a medium height and build and a small amount of hair above his upper lip and was driving a white van.

He was wearing a blue top with brown pants.

Detectives from the Bass Coast Crime Investigation Unit are calling on the public for help and would like to speak to anyone who may have witnessed the incident or any suspicious activity in the area around that time.

Police are also searching for an older model, white Mitsubishi van with a red badge on the front.

Anyone with information please call Crime Stoppers on 1800 333 000 or visit www.crimestoppers.com.au