A state of emergency has been declared in the ACT amid worsening fire conditions.

The decision was made after the Orroral Valley fire was upgraded to a Watch and Act level.

The fire was reportedly sparked by the landing lights of a Defence Force helicopter, which created enough heat to set the grass on fire and is now burning out of control.

This is the first time a state of emergency has been declared in the ACT since the 2003 bushfires.

A total fire ban is currently in place.