The incident knocked out power to subways, stores and Broadway theatres, but the city's main utility began restoring power several hours later.

Con Edison and New York officials say power has been restored to hundreds of thousands of customers. No deaths or injuries were reported due to the blackout.

Officials said it began at 6.47pm on Saturday, darkening a stretch of the city 42 years to the day from a major 1970s blackout that sparked rioting and looting.

Shouts of celebration could be heard in parts of Manhattan as power was restored, bringing lights and air conditioners back to life.

The cause of the outage was unclear, McAvoy said, adding "it does not appear related to excessive load".

A Reuters witness in the area reported hearing an explosion around 7pm, and a fire department spokesman said firefighters were on the scene of a transformer fire.

Sidewalks in Times Square that are usually crowded with tourists on a balmy summer Saturday night were overflowing as at least some Broadway theatres cancelled performances. The lights of nearby Radio City Music Hall were dark.

In an attempt to cheer customers, the cast from the musical Come From Away performed a song in front of the stage door. Hadestown cast members also staged a street-side performance.

With traffic lights out, cars and taxis jammed intersections as emergency vehicles and fire engines with sirens blaring tried to pass. In some places, civilians stepped in to direct traffic.

New York has endured large-scale blackouts before, most recently following Superstorm Sandy in 2012 as well as the widespread 2003 blackout across the US Northeast that left most of the city without power for a day.

Saturday's outage occurred on the 42nd anniversary of a New York blackout that crippled the city during a heat wave on July 13, 1977. Power was not restored until the next day.

Australian Associated Press