A large, fast-moving and uncontrolled grassfire north of Melbourne is growing and heading towards more towns.

The blaze started at Flowerdale, about 90 minutes from the Victorian capital, on Tuesday afternoon and is burning north towards Yea.

Waterbombing aircraft were used overnight, and it’s believed no homes have been impacted, but the full extent of damage to fences and sheds is unknown.

The fire is more than 700 hectares in size and burning across steep, inaccessible terrain towards forested areas.

An emergency warning is in place for Flowerdale, meaning it is too late for many residents to leave.

However, those located between Dairy Creek Road and Handleys Road and Upper King Parrot Creek Road and Landmark Lane have been told to go before conditions get worse.

Smoke is visible across the areas, and an incident control centre has been set up at Alexandra.

More than 50 CFA units are fighting the blaze with support from Forest fire Management.

An image posted to social media by the Wonga Park CFA on Tuesday night showed thick terrain glowing bright orange against the night sky.

A heatwave warning has been issued for Victoria, and temperatures are expected to reach more than 30 degrees for the next three days.