Religious leaders from the Christian, Hindu, Buddhist and Jewish faiths led the crowd in prayers for peace at the rally to mark Palm Sunday.

The protestors then marched through the city centre chanting "bring the troops back home" and "US out of Iraq".

The demonstration passed off peacefully, unlike recent student demonstrations where Middle Eastern youths clashed with police.

While the event, and another march of 5,000 people in Melbourne, did not attract the 100,000-plus crowds seen at rallies before the war began, organisers said it still showed significant opposition to Australia's role in the war.

"People do not want Australian troops to be part of America's blatant power play," Greens politician Ian Cohen said.

He denied numbers were down because people largely felt the fighting was over.

Opinion polls have shown an almost even split among Australians on the question of whether they support the war, with a narrow majority moving to back the government's position once hostilities were declared.

Meanwhile, two Australian Hercules planes left Sydney on Sunday carrying almost seven tonnes (7.7 short tons) of urgently needed medical supplies for hospitals in Baghdad.

With reports of looting in the hospitals, Australian Defence Force spokesman Brigadier Mike Hannan said a military nurse and Australian commando guards would accompany the supplies to ensure they reached the intended receipients.

"Our understanding of the situation at the moment is that there are plenty of medical professionals in Baghdad and in Iraq and the medical standards are excellent," Hannan told reporters.

"The problem they've got is that they just don't have the equipment, the stuff they need to do their job, and that's the real focus at the moment."

Another Hercules arrived in Baghdad Sunday carrying medical supplies from the Australian warship HMAS Kanimbla, which is stationed in the Gulf.

SPACE.WIRE