Less than a quarter of New Yorkers voted on Tuesday

Less than a quarter of the New York electorate voted in Tuesday's mayoral election that swept progressive Democrat Bill de Blasio to power, according to preliminary results.

De Blasio, 52, is the first Democrat elected mayor of the largest US city in 20 years and replaces billionaire Michael Bloomberg who has been in office since 2002.

He won a stunning landslide victory of 73.3 percent of votes cast compared to 24.3 percent for his Republican rival Joe Lhota, according to results from 99 percent of polling stations.

But of the 4.6 million registered voters in New York only 1.02 million actually cast a ballot, based on those results.

Around 752,000 New Yorkers voted for de Blasio. The city has around 3.1 million Democrat voters.

Some 250,000 voted for Lhota out of 451,000 Republican voters.

Another 24,000 voters went for alternative candidates, led by independent Adolfo Carrion, who won 8,200 votes or 0.8 percent of the vote.

De Blasio, who thrust his black, former-lesbian, poet wife and their teenage children to the fore of his campaign, promises to redress huge inequality but has warned it will be an uphill task.

He formally takes office on January 1.