Democrat Bill de Blasio has been elected the 109th mayor of New York City, interrupting two decades of republican rule over the 'Big Apple'.

De Blasio, previously the city's public advocate, beat his republican challenger Joe Lhota, the former chief of the metropolitan area's transit agency, by a landslide.

The 52-year-old won 73% of the vote against the 24% recorded by Lhota, reflecting the overwhelming lead in the polls he had been holding for weeks.

De Blasio succeeds Michael Bloomberg, who leaves the mayor's office after 12 years in charge.

The new incumbent - at 6ft 5in the tallest mayor in New York's history - ran a campaign in sharp contrast with the image of his billionaire predecessor.

De Blasio rallied against economic inequality in the city, which he said had been split into two halves - one rich, the other working class - by pro-business Bloomberg.

"We are united in the belief that our city should leave no New Yorker behind," De Blasio, flanked by his family, said in his victory speech. "The people of this city have chosen a progressive path, and tonight we set forth on it together as one city."

His victory owed much to his down-to-earth approach and multi-ethnic family. Indeed his campaign received a major boost from a campaign ad featuring his son Dante, a 15-year-old with a big Afro haircut.

"We have no illusions about the task that lies ahead. Tackling inequality isn't easy, it never has been and never will be," De Blasio said.

"The challenges we face have been decades in the making and the problems we set out to address will not be solved overnight."