LOS ANGELES (AFP) - Tens of thousands of protestors marched through Hollywood on Friday to mark the centenary of the massacre of some 1.5 million Armenians by Ottoman forces.

"We demand justice," read placards carried amid a sea of red, blue and orange Armenian flags along Sunset Boulevard, as demonstrators marched towards the Turkish consulate.

Los Angeles is home to the largest Armenian community in the United States, with nearly 200,000 living in the city and nearby suburb of Glendale, where about a third of the population is Armenian.

Organisers put the turnout at 50,000, while police told AFP that 30,000 protesters were on the streets.

The march began with a ceremony attended by city officials dedicating Armenian Genocide Memorial Square on a junction of Hollywood Boulevard in a district known as Little Armenia.

The memorial will "show that the city of Los Angeles recognises the history of the Armenian Genocide, as well as the impact the event had on the Armenian community," said local councilman Mitch O'Farrell.

"We demand recognition of the Armenian genocide," read a banner pulled along by one of two light aircraft circulating in the skies above the massive LA march.

Last month, US lawmakers introduced a resolution urging President Barack Obama to recognise mass killings of Armenians as genocide, but he declined, calling it a "terrible carnage" in comments on Thursday.

Armenia says an estimated 1.5 million people were killed by Ottoman forces in 1915, and has labelled the massacre a genocide.

Modern Turkey has always rejected the term, putting the toll at 500,000 and blaming their deaths on war and starvation.