Five people were arrested as the Olympic flame arrived in Australia on Wednesday and officials said they were prepared for more protests on the latest leg of the troubled global torch relay.
The flame has become the focus of international demonstrations against China's role in Tibet and the Olympic host's human rights record, and has attracted angry protests in Europe and the US.
Even before a chartered airliner carrying the flame touched down at a military airfield in Canberra under tight security, protesters used the Sydney Harbour Bridge as a backdrop for their pro-Tibet message.
A man and a woman attempting to unfurl a banner and a Tibetan flag on the iconic landmark were arrested hours after lasers beamed pro-Tibet slogans including "Don't torch Tibet" onto one of the structure's pylons.
A police spokeswoman told AFP the two were detained by security officers and faced a fine for trying to attach their banner to the bridge without a permit.
Later, Sky News reported that three people were taken into custody after raising a pro-Tibet banner on a prominent billboard in the city's King's Cross nightlife district.
Australian officials have shortened Thursday's relay route through the capital Canberra over concerns about security at an event expected to attract thousands of pro-China supporters and pro-Tibet demonstrators.
Barriers have been erected along the 16-kilometre (10-mile) route and more than half of the city's police force will be on patrol.
Australian Capital Territory Chief Minister Jon Stanhope said it would be "naive in the extreme" to think that protesters would not try to use the relay to push their message but he did not regret the torch's presence in Canberra.
"I am not regretful, I just have some anxieties around some of the implications," he told a press conference.
Police said they were confident that security would be adequate, despite a dispute between Australian and Chinese officials over the role of the torch's Chinese escorts.
Beijing Olympics torch relay spokesman Qu Yingpu backed Chinese ambassador Zhang Junsai's comments that the escorts could use their bodies to protect the flame if necessary.
But Stanhope said this condition had not been agreed to by the Australian government and that security would be solely the responsibility of local police.
"We do have some issues around communications," he said.
The torch, symbol of the Beijing Games, is on the Asian stretch of a world tour that began with protests in Greece when the flame was lit in late March.
The relay of the Olympic flame from Athens is a tradition introduced in the modern Olympics era only at the Berlin Games in Nazi-ruled Germany in 1936.
The violence which has greeted the torch in some cities and the strict security precautions taken have raised the prospect of the global relay being discontinued in the future.
At protests in London and Paris demonstrators tried to wrest the torch from bearers while in the US protesters complained about China's rule in Tibet and its human rights record.
But Qu said despite the controversy, the journey had been a success.
"It's like everything else -- we've had our ups and downs but we are quite easy with that," he said.
"We see many smiling faces in many cities. Even in London and Paris we also see smiling faces."
The torch, which was kept at an undisclosed location in Canberra ahead of Thursday's relay, is due in Japan on April 26.