Tens of thousands of pro-Palestinian protesters including WikiLeaks founder Julian Assange marched across the Sydney Harbour Bridge on Sunday, closing the world famous landmark.

Assange, who returned to Australia last year after his release from a high-security British prison, was pictured surrounded by family and marching alongside former Australian Foreign Minister and New South Wales Premier Bob Carr.

France, Britain and Canada have in recent weeks voiced intentions to recognise a Palestinian state as international concern and criticism have grown over malnutrition in Gaza.

Australia has called for an end to the war in Gaza but has so far stopped short of a decision to recognise a Palestinian state.

The pro-Palestinian crowd braved heavy winds and rain to march across the bridge, chanting "ceasefire now" and "free Palestine".

New South Wales police said it had deployed hundreds of extra staff across Sydney for the march.

Mehreen Faruqi, the New South Wales senator for the left-wing Greens party, told the crowd gathered at central Sydney's Lang Park that the march would "make history" and called for the "harshest sanctions on Israel". She also criticised New South Wales premier Chris Minns for saying the protest should not go ahead.

Dozens of marchers held up banners listing the names of thousands of Palestinian children killed since the Gaza war broke out.

Assange did not address the crowd or talk to the media. (AFP)