Inner Sydney terrace up in flames

Authorities are investigating a fire that ripped through a terrace house in inner Sydney.

Fire crews arrived at the Surry Hills property after 4am on Monday to find it well alight, NSW Fire & Rescue spokesman told AAP.

Cleveland Street was closed in both directions as firefighters put out the blaze.

In a separate incident, fire crews had to force their way into a townhouse in the inner-west suburb of Burwood about 1.20am following reports smoke was billowing from the building.

No one was inside either property when they went up in flames.