A 5.0-magnitude earthquake has rattled residents in southwestern Victoria with thousands of people reporting to have felt the early morning tremor.

Geoscience Australia said the earthquake struck at 2.11am on Sunday near Colac in the Great Otway National Park, about 165km from Melbourne, at a depth of 7km.

The seismologists had originally measured the quake as being of magnitude 4.7 but later revised this to 5.0 and moved the epicentre from Apollo Bay.

An aftershock with magnitude 3.5 was recorded at Apollo Bay at 5.44am, Geoscience Australia said.

Victorian emergency services said no injuries had been reported and the earthquake appeared to have resulted in little or no damage.

More than 4420 people reported feeling the earthquake by 3.30am, including many residents in the Victorian capital.

Geoscience Australia said the quake was felt as far north as Bendigo and as far south as King Island.

—AAP