At least 15,000 people have marched through Sydney to show their opposition to conflict in Iraq in what was one of the largest anti-war demonstrations of recent years.

Australia's chief Islamic cleric Sheikh Taj Aldin al-Hilali joined the rally

Protesters also took to the streets in Canberra and Adelaide and rallies are planned for other cities, including Melbourne, as part of a co-ordinated weekend of events to call for diplomacy not military intervention.

Australian Prime Minister John Howard has backed the tough line on Iraq taken by the United States and has pledged to send troops to back any campaign.

But the BBC's Dominic Hughes in Sydney says many of the protesters are concerned that the US is motivated by a desire to seize Iraqi oil rather than by security concerns.

He adds that public opinion polls show Australians want any action to be led by the United Nations and to come only after the weapons inspectors have had a chance to do their job.

We must not confuse the need to rid ourselves of terrorism with a pre-emptive strike on Iraq

Union leader Sharan Burrow

Australia's supreme Islamic cleric, Sheikh Taj Aldin al-Hilali, joined other religious leaders as well as politicians and showbusiness personalities on the Sydney demonstration.

Australian Council of Trade Unions president Sharan Burrow told the crowd that the nation needed to send a message to the government that it was not acceptable for Australia to be dragged into a US-led military attack.

"We must not confuse the need to rid ourselves of terrorism with a pre-emptive strike on Iraq," she said.

"It's a threat to world peace that must be resisted."