More than half a million people in the US state of Oregon are fleeing deadly wildfires that are raging across the Pacific Northwest, authorities say.

Fanned by unusually hot, dry winds, dozens of infernos are sweeping the state, and at least one is being treated as suspected arson.

Governor Kate Brown said the exact number of fatalities was not yet known, though at least four were confirmed.

More than 100 wildfires are currently scorching 12 western US states.

Oregon, California and Washington have borne the brunt of the wildfires, which have in several cases destroyed entire towns. In California alone, at least 10 deaths have been confirmed.