Fears for missing 5-year-old Vic boy

A mother is believed to be on the run with her young son, who was last seen at a home in Melbourne's northern suburbs.

Police believe Sarah Jones, 35, is with five-year-old Nicholas Jones after he was last seen at a home on Genoa Avenue, Reservoir, about 9pm (AEDT) on Friday.

Police say they have have concerns for Nicholas's welfare. He has short blond hair, fair skin and a broken front tooth and was last seen wearing red and blue Spiderman pyjamas and carrying a blanket embroidered with brown teddy bears.