Man badly burned in Sydney unit fire

A man has suffered serious burns and a number of units have been destroyed in a fire in Sydney's northwest.

Emergency services were called to the blaze in Ermington at about 7pm yesterday following reports of an explosion at a unit.

Firefighters extinguished the blaze which had spread to neighbouring units in the same complex, prompting the evacuation of more than 40 people.

A 51-year-old man from the unit where the fire originated suffered serious burns and was taken to hospital along with a man from another unit who suffered smoke-inhalation.

Police say an investigation is underway but it has not yet been determined if the fire was suspicious or not.

With AAP.