The pro-Palestinian supporters gathered outside the State Library at 1pm before marching up Swanston, Collins and Spring Streets, re-converging in front of the Victorian Parliament.

Among the speakers was David Taylor, a representative of Jews Against Israeli Apartheid.

Taylor told the crowd: ‘‘We have to take power and tell the people what’s going on Gaza.’’

Protester Louise O’Shea told Fairfax Media: ‘‘There are a lot of Jews around the world that oppose the crimes Israel are committing supposedly in the names of the Jewish people. I think what motivates the Australian state and its backers, like the US government, is not anything to do with protecting the Jewish people.

‘‘It’s about the economic and political interests that western companies and the western political establishment have; the energy supply that comes from the Middle East; the trade routes that go through the Middle East; the natural resources in the region – that’s what motivates them. That’s what’s always motivated them.’’

Rally organiser Kim Bullimore estimated the crowd swelled to 5000 after marching to Spring Street.

Ms Bullimore said the purpose of the demonstration was to ‘‘protest both Israel’s massacres in Gaza and the Abbott government’s support for Israel’s war crimes’’.

Today’s protest was the third in as many weeks. Ms Bullimore has arranged another for August 1st.

‘‘We organised the first one because of the crackdown in Gaza and as long as the offensive keeps going, there will be rallies,’’ she said.

‘‘One of our demands was to call on the Abbott government to break ties with Israel ... what Israel is doing is war crimes, no matter how many leaflets they drop or warnings they give [before bombing].’’

Protesters carried hundreds of black balloons and signs accusing Israel of terrorism and war crimes. One girl, who appeared to be aged around eight or nine, carried a home-made banner that declared: ‘‘Israel, we will meet you on judgment day.’’

Several unrelated activist groups – including fundamentalist Christians, anti-abortionists and people raising awareness of Chinese organ harvesting – tried to draw support for their causes, but with little success.

‘‘We’re here to condemn Israel’s atrocious slaughter of the Palestinians of Gaza,’’ said protester Emma Dook. ‘‘I’m also here to show solidarity with the Palestinians of the West Bank, who have bravely come out [in protest on Friday].’’