CANBERRA, Australia — The Australian leg of the Olympic torch relay began yesterday, shortly after minor protests erupted among supporters and detractors of China’s government that left two people detained.

Thousands of people lined the planned relay route on the cool but sunny autumn day as police manned crowd-control barriers and vowed that nothing would stop the torch from completing its trip through Australia’s capital.

The relay began without major incident as a half-dozen police officers, in running pants, T-shirts, and baseball caps, formed a loose cordon around the runner. Overhead, an airplane sky writer wrote the words “Free Tibet” in giant white letters.

Organizers of Australia’s portion of the relay worried that chaotic demonstrations that marred the event elsewhere could be repeated. Protests of China’s human rights record and its crackdown on anti-government activists in Tibet have turned the relay into a contentious issue for the Olympic movement. Many countries have changed routes and boosted security along the flame’s six-continent journey to the August 8-24 games in Beijing. In Nepal, authorities forced an American mountaineer with a “Free Tibet” banner in his bags off Mount Everest. Chinese climbers carrying the Olympic torch plan to ascend their side of the world’s tallest peak in the early days of May.