“But it’s unlikely … that it was fired from Russia.

“I’m going to make sure we figure out exactly what happened. Then we’re going to collectively determine our next step as we investigate and we proceed.”

It was not immediately clear whether Biden was suggesting that the missile hadn’t been fired by Russia at all. Ukraine still maintains stocks of former Soviet and Russian-made weaponry, including the S-300 air-defence missile system.

Biden said there was “total unanimity” among his fellow leaders at the meeting in Bali’s Nusa Dua district.

He described the latest wave of Russian missile attacks as “totally unconscionable”.

“At the moment when the world has come together at the G20 to urge de-escalation, Russia continues to escalate in Ukraine,” he said. “While we’re meeting there were scores and scores of missile attacks in western Ukraine.”

G7 leaders also offered their full support to Poland’s investigation following the emergency talks.

“We condemn the barbaric missile attacks that Russia perpetrated on Ukrainian cities and civilian infrastructure,” they said in a statement released by the European Commission.

“We discussed the explosion that took place in the eastern part of Poland near the border with Ukraine. We agree to remain in close touch to determine appropriate next steps as the investigation proceeds.”

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Japanese Prime Minister Fumio Kishida told the meeting he was “very concerned” about the events, according to a statement released by Tokyo’s foreign ministry.

“Developments in Ukraine affect the core of international order and are inseparable from security affairs in the Indo-Pacific region,” Kishida said.

The heads of state and governments gathered on the Indonesian island also paid a visit to a mangrove forest on Wednesday morning, in a demonstration of the need to combat the effects of climate change.

They were then due to meet for the third and final joint leaders’ session at the two-day summit.

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Russian Foreign Minister Sergei Lavrov will not attend, having flown out of Bali on Tuesday night after the first day of meetings. Lavrov said before departing that Moscow would be represented by a finance minister on the last day when negotiations were set to continue about the language of a proposed G20 joint statement.

A draft version leaked on Tuesday said, “most members strongly condemned the war in Ukraine, and stressed it is causing immense human suffering and exacerbating existing fragilities in the global economy”.

Lavrov accused Western nations of trying to politicise the statement and said Russia had demanded that if the war was covered in the communiqué, it must note that not all countries were in agreement.