UPDATE: The Russian president's press secretary, Dmitry Peskov, has denied reports saying Putin plans to leave the G20 summit ahead of time due to pressure over Ukraine.
"The G20 summit ends tomorrow (on Sunday) and Vladimir Putin will surely leave it – when all the work is finished, the president will leave. The report by Reuters is wrong. The issue of the sanctions is being widely and actively discussed during all bilateral meetings, but there’s no pressure,” Peskov told Kommersant FM radio.
Vladimir Putin faced a chorus of criticism Saturday at the G20 world leaders' summit, apparently resulting in his announcement that he would be leaving early.
As the escalating conflict between Russia and Ukraine threatened to overshadow talk of global economics, a Russian official told Reuters that Putin planned to skip a working session on Sunday at the two-day summit in Brisbane and bring forward his departure because he needed to attend meetings in Moscow.
Russia denied it was involved in a recent escalation of military activity in Ukraine, where fighting has claimed more than 4,000 lives, but faced strong rebukes from Western leaders, including US President Barack Obama and Canadian Prime Minister Stephen Harper.
Putin received a less-than-warm welcome from Harper when he approached Harper for a handshake.
"I guess I'll shake your hand, but I have only one thing to say to you: You need to get out of Ukraine," Harper told Putin, according to the prime minister's spokesman, Jason MacDonald.
As for Putin's reaction? "I can say that he did not respond positively," MacDonald said in an email, declining to give further details.
David Cameron, meanwhile, accused Putin of "machismo" after the Russian president rather unsubtly sent an entire fleet of warships to the Australian coast to coincide with the gathering of the G20 group of world leaders in Brisbane.
The deployment of the cruiser Varyag and three support vessels on exercises in the Coral Sea has sparked outrage in Australia, with Prime Minister Tony Abbott describing it as part of a "regrettable pattern" of Russian military assertiveness which appeared to be trying to recreate the "lost glories" of the Soviet Union.
Cameron described the vessels' presence as an attempt to project "international machismo" but played down their significance, joking: "I didn't feel it necessary to bring a warship myself to keep myself safe at this G20, and I'm sure that Putin won't be in any danger."
European Union President Herman von Rompuy said that while the Ukraine conflict was not on the agenda of the Group of 20 wealthy and developing economies, the topic would be discussed between President Barack Obama and EU leaders in Brisbane ahead of a European Union decision on further sanctions against Moscow.
"We will continue to use all diplomatic tools including sanctions at our disposal," von Rompuy told reporters. "The EU foreign ministers will on Monday assess the situation on the ground and discuss possible further steps."
"We need to avoid a return to a full-scale conflict," he said.
In a speech to a Brisbane university audience, Obama said that the United States was a leading voice in opposing Russian aggression in Ukraine, which he described as "a threat to the world."
He referred to the shooting down on July 17 of a Malaysia Airlines jet by a missile suspected to have been fired by Russian-backed rebels in eastern Ukraine with the loss of 298 lives, including 38 Australian citizens and residents.
"As your ally and friend, America shares the grief of these Australian families and we share the determination of your nation for justice and accountability," Obama said.
Von Rompuy called for both sides to abide by the cease-fire agreement between Ukraine and the rebels that was signed in Minsk, Belarus, in September.
Russia must use its influence on the rebels to ensure they comply with the Minsk agreement, stop the flow of weapons and troops from Russia and withdraw Russian troops already in Ukraine, von Rompuy said.
US Secretary of State John Kerry issued a similar call. The State Department said Kerry expressed "grave concern" about increased Russian support for the separatists and called for the implementation of the Minsk agreement, including a cease-fire, border monitoring, release of all hostages and a return to dialogue during a discussion with Russian Foreign Minister Sergey Lavrov.
Von Rompuy declined to comment on the likelihood of the EU deciding to ratchet up sanctions.
"Russia has still the opportunity to fulfil its Minsk agreements and chose the path of de-escalation, which could allow sanctions to be rolled back," he said. "If it does not do so however, we are ready to consider additional action."