Ring of fire: Australian state declares emergency as wildfires approach Sydney

FILE PHOTO: A fire blazes across bush as seen from Mount Tomah in New South Wales, Australia December 15, 2019 in this still image obtained from social media video. NSW RFS – TERRY HILLS BRIGADE/via REUTERS

SYDNEY (Reuters) - Australia's most populous state declared its second emergency in as many months on Thursday as extreme heat and strong winds stoked more than 100 bushfires, including three major blazes on Sydney's doorstep.

A day after Australia recorded its hottest day on record, thick smoke blanketed the harbour city, shrouded the Opera House and brought many outdoor activities to a halt.