VicRoads said it had closed the Freeway from Sydney Road to Cooper Street until further notice while firefighters battle to control the blaze. Drivers are advised to use the Old Hume Highway as an alternative.

Three properties are under threat from a fast-moving grass fire in the Donnybrook area north of Melbourne, while homes are under threat from two out-of-control fires in the west of the state.

The Country Fire Authority has issued a "emergency warning" warning on the blaze that started near Donnybrook Road on Melbourne's northern fringe at 1.20pm.

Under this level alert, according to the CFA website, ‘‘there is a risk to lives and homes, follow your bushfire survival plan. If you plan to leave, or you are not prepared and there is a safer place near by, leave now if it is safe to do so.’’

The fire was described as being in the Wollert area north of Melbourne.

The CFA said the fire was travelling in a southerly direction towards Vearings Road, Craigieburn Road East and Epping Road and was ‘‘expected to impact immediately’’.

‘‘This grassfire is approximately 200 hectares in size and is out of control,’’ the CFA warned.

It travelled south towards Craigieburn Road and crossed Summerhill Road.

Twenty firefighting trucks and two water-bombing helicopters are fighting the blaze, near Epping.

A CFA spokesman said three properties on Vearings Road were in the path of the fire.

Anyone living in the area is urged to follow their bushfire survival plan, monitor media and leave if it is safe to do so.

Meanwhile, eight homes remain under threat from a 1200-hectare bushfire burning out of control 30 kilometres north of Dunkeld near the Grampians National Park.

The CFA has issued an Emergency Warning urging residents to follow their bushfire survival plans.

The fire was described as large, fast-moving and travelling in a south-easterly direction.

This fire was expected to reach Victoria Valley before 7pm tonight and was creating spot fires about a kilometre ahead.

A CFA spokeswoman said volunteer firefighters were working with residents to protect their properties amid extreme temperatures and a northerly wind gusting  up to 45 km/h.

She said firefighters were preparing for a southerly change around 9pm.

The CFA website reported that the nearby Clutterbucks Road fire had broken containment lines and was also threatening the Victoria Valley.

The spokeswoman said there was a chance the two fires could  merge.