BRISBANE: Australia's prime minister tried to get his bickering G20 colleagues to loosen up at summit talks in the laid-back city of Brisbane on Saturday before hosting a lunch of prawns and pavlova in the baking heat.

The conservative Australian leader, who held a private leaders-only retreat ahead of formal talks that will focus on economic growth, energy security and tax reform, called for the high-powered meeting to be open and friendly.

“The people around this room are... the most powerful and influential people in this world,” Abbott told the likes of United States President Barack Obama, Chinese leader Xi Jinping and Russian strongman Vladimir Putin.

“We may not always be able to agree but I hope we can at least be open with each other,” he said, urging his fellow leaders to speak from the heart, not the “script”.

“And if we could use first names, that would be good as well. Because whatever disagreements we might have, it helps if there can at least be personal warmth amongst us.”

Abbott then hosted an outdoor lunch with tents as shade as temperatures soared above 30 degrees Celsius (86 degrees Fahrenheit).

On the menu was the Australian barbecue favourite of king prawns as well as rock oysters, smoked spiced lamb and Tasmanian ocean trout. The meal was completed by pavlova, the classic meringue and cream dessert claimed by both Australia and New Zealand.

The leaders' retreat was seen as an “ice-breaker” ahead of the formal G20 talks later Saturday and Sunday, which come as Abbott, Cameron and Obama have spoken out strongly against Russia over the Ukraine conflict.

Putin has faced a frosty reception from Western leaders over the shooting down of Malaysia Airlines Flight MH17 over Ukraine in July, killing 298 people, including 38 Australian residents.

The crisis in Ukraine was one of many sparking protests in Brisbane on Saturday, with up to 1,000 people taking to the streets for various causes including climate change in rallies police praised as peaceful.

“I'm here to bring the attention the fact that the (Australian) prime minister has not brought climate change to the G20,” said one protester, June Norman.

No beach for Obama

Brisbane's G20 has been distinctly antipodean, with the leaders' spouses taken to feed koalas and kangaroos on Saturday morning while enjoying a demonstration of sheep shearing, a reference to Australia's wool industry.

Despite the sober nature of the talks, there have been light-hearted touches with Cameron joking about Abbott's love of exercise and Obama referencing sharks and crocodiles in an address to a Queensland university.

“I love Australia. I really do. The only problem with Australia is that every time I come here I've got to sit in conference rooms and talk to politicians instead of going to the beach,” Obama said.

Angela Merkel was another leader taking the long-haul visit in her stride, charming locals by visiting a Brisbane pub on Friday night.

Photos of the German Chancellor meeting locals at a popular bar strip circulated on social media, cheering a city in security lock-down with thousands of police on the streets and huge wire fences erected around venues and surrounding precincts.

“We expected her to be ushered inside (the bar) really quickly. But she didn't, in fact, she chose to come over,” one woman, who did not want to give her name, told the Australian Broadcasting Corporation.

“She was very kind. My friend said 'Oh, can I get a quick selfie?'. She (Merkel) checked with her security detail, they gave her a nod and she popped in for a quick photo."