Police have appealed for witnesses after a spate of suspicious fires in inner Brisbane overnight.

Emergency services were called to the first incident at 9:30pm, where a house on Franklin Street in Highgate Hill was on fire.

The blaze was extinguished.

However, a short time later crews were called to another fire at a home on the same street.

That house was extensively damaged.

While at the scene, a third fire was reported at a unit block on Hampstead Road, around the corner from Franklin Street.

Multiple cars parked underneath the building were damaged.

A crime scene has been declared on each street.

No-one was injured.

–ABC