US President Joe Biden said Wednesday it was "unlikely" a missile strike on Poland was launched from Russia, speaking after emergency talks with allies in Bali about the deadly attack.

Biden huddled with G7 and NATO partners on Wednesday, hours after the strike that killed two people in a Polish village near the border with Ukraine.

"We agreed to support Poland's investigation into the explosion," Biden told reporters after the hastily arranged gathering on the sidelines of the G20.

"We're going to make sure we figure out exactly what happened… and then we're going to collectively determine our next step."

Asked if the missile had been fired from Russia, Biden said there was "preliminary information that contests that".

"It's unlikely… that it was fired from Russia. But we'll see."

The explosion in Poland, a NATO member, immediately sparked concerns that the alliance might be drawn directly into Russia's nearly nine-month war against Western-backed Ukraine.

UN Secretary-General Antonio Guterres, also in Bali, warned it was "absolutely essential to avoid escalating the war in Ukraine".

Polish President Andrzej Duda also urged calm, saying there was no "unequivocal evidence" of where the missile came from, and that he saw it as an "isolated" incident.

"Nothing indicates to us that there will be more," he said.

The French presidency urged "utmost caution" on the origin of the strike, with an official saying many countries had the same missiles and warning of the "significant risks of escalation".

'Slap in the face'

Poland is now expected to request urgent consultations under Article 4 of the NATO Treaty, which is invoked when any member feels their "territorial integrity, political independence or security" are at risk.

Ukrainian President Volodymyr Zelensky quickly blamed Moscow for what he termed "Russian missile terror".

The incident came after Russia launched a wave of missile strikes across Ukraine on Tuesday that left millions of households without power.

Biden on Wednesday called those attacks "barbaric", and Zelensky described them as a "slap in the face" for the G20.

The summit has been dominated by the conflict in Ukraine, with members struggling to find common ground on Russia's invasion of its neighbor.

In a joint statement issued Wednesday, leaders came together to condemn the war's effects but remained divided on apportioning blame.

The summit has shown however that even Russia's allies have limited patience with a conflict that has inflated food and energy prices worldwide and raised the specter of nuclear war.

All members, including Russia, signed off on a line saying that the "war in Ukraine" — which Moscow refuses to call a war — has "adversely impacted the global economy".

And Moscow also agreed that "the use or threat of use of nuclear weapons" was "inadmissible", after months of President Vladimir Putin making such threats.

'Not a political forum'

Russia's G20 allies China, India, and South Africa have so far refrained from publicly criticizing Putin's war, and the statement is replete with diplomatic fudges.

It says "most members strongly condemned the war in Ukraine," but adds that there were "other views and assessments".

Putin shunned the gathering, instead sending his pugnacious Foreign Minister Sergei Lavrov, who left the summit Tuesday night, skipping the final day of talks.

The United States and its allies have used the summit to broaden the coalition against Russia's invasion and scotch Moscow's claims of a war of East versus West.

Host Indonesia, meanwhile, has walked a tightrope, keen to end its G20 presidency with the relative triumph of a joint statement from the fractured group.

It has declined to criticize Russia, and invited Zelensky to address the summit, including with a speech Tuesday in which he urged leaders to end the war and "save thousands of lives".

At the final session on Wednesday, Indonesian President Joko Widodo also begged counterparts to "stop the war", saying the conflict would prevent a global recovery.

But he dodged questions about the conflict during a walkabout with leaders at a mangrove hours after the Poland strike and Russia's latest wave of attacks in Ukraine.

"The G20 is an economic forum, a financial forum, and diplomat forum, not a political forum. So here we talk about the economy," he told reporters.