Vladimir Putin's early exit from a G20 summit in Australia after an icy reception from world leaders may further stoke Russia-West tensions and lead to renewed fighting in Ukraine, analysts said.

Western leaders piled huge pressure on the Russian president at the Group of 20 meeting in Brisbane, with host Tony Abbott calling on Putin to "atone" for the shooting down of Flight MH17 over rebel-held eastern Ukraine and Britain's David Cameron branding him a "bully".

Analysts said Putin's apparent anger at his treatment by his fellow leaders could worsen the crisis in Ukraine.

"If he is leaving irritated, just wait for the fighting in Ukraine to intensify," independent analyst Stanislav Belkovsky told AFP.

Putin, who prides himself on his stamina, cited the "need to sleep" and a long flight home as his reasons for leaving the summit before the final communique was issued.

Despite the baking heat in Brisbane, the chill in the air was unmistakable, with Western leaders threatening new sanctions if fighting in Ukraine intensifies.

Australian tabloid The Courier-Mail called Putin "the black sheep of the G20 family," while Russian media complained that Western leaders went out of their way to ostracise him.

"At the G20 Australian hosts tried to humiliate Vladimir Putin in every way possible," pro-Kremlin magazine Expert said.

Armed with the Forbes title of "the most powerful man in the world" and approval ratings over 80 percent, Putin arrived in Australia with a flotilla of Russian navy vessels in tow.

He and the West had not been expected to reach a breakthrough over Ukraine, yet few had expected hostilities to break out into the open.

In recent years Putin has stolen the limelight at international gatherings, setting himself up as an outsider at G8 gatherings as the Kremlin agenda grew increasingly at odds with Western interests.

But the walkout in Brisbane took tensions to a whole new level.

Analysts said that Western leaders' increasingly vocal criticism of the Kremlin and Putin's abrupt departure indicate that neither side was interested any longer in maintaining even a patina of civility.

'Outcast? Yes'

Fyodor Lukyanov, chairman of the Kremlin-connected Council on Foreign and Defence Policy, warned that Western criticism might force Putin to harden his position.

"We are witnessing a further radicalisation of the positions of some Western countries, first and foremost North America and Australia, which is the summit host," Lukyanov said on radio.

"There is no desire on their part to somehow soften this, on the contrary this is spilling into the public sphere. Well, the reaction is predictable -- Russia will also harden its stance."

Lilia Shevtsova, an analyst at the Brookings Institution, said as Russia's confrontation with the West grew bigger, Moscow was becoming increasingly dependent on China.

"An outcast? Yes, the APEC in Beijing and the G20 in Brisbane confirmed that Putin had become an outcast," she said on Facebook.

"A dependent outcast -- world politics does not know a combination that would be more explosive."

Ahead of the summit, US President Barack Obama said Russia's aggression against Ukraine was "a threat to the world" and called the shooting down of MH17 in July "appalling".

Australia's Abbott accused Putin of trying to relive the "lost glories of tsarism," while Britain's Cameron said Putin was undermining Russia's own interests.

Putin was also apparently rebuffed by Canadian Prime Minister Stephen Harper when the Russian leader approached him.

"Well, I guess I'll shake your hand, but I only have one thing to say to you: you need to get out of Ukraine," said Harper.

The West has accused Russia of sending fresh military hardware into eastern Ukraine, fuelling fears of a return to all-out conflict. Russia has denied the claim.

"De-escalation did not pan out," said Gazeta.ru.

"Summit G19+1 in Australia," quipped a prominent satirical Twitter account in Russia.

'More capricious, more attention'

Analysts also said Putin's walkout on the Western leaders would play well with his supporters back home.

"All the gestures of the Russian leader are aimed at the so-called Putin majority," Konstantin Kalachev, head of the Political Expert Group, told AFP.

He said Putin's attitude would be interpreted by his backers as: "What does Russia's national leader have to talk about with the rotten West?"

Kalachev also pointed out that by dispensing with diplomatic niceties Putin might be intentionally setting himself apart from other leaders.

"The more capricious, the more attention."

Observers also pointed to Putin's charm offensive at the APEC summit in Beijing ahead of the G20 where he caused an uproar by wrapping China's first lady Peng Liyuan in a shawl.

While some chalked up the gesture to old-school gallantry, others said it was the latest sign that the Russian leader considered himself above normal conventions.

"This is also a hint at his own power," wrote journalist and former diplomat Alexander Baunov.