G7 leaders pose for a group photo with the outreach guests at the G7 summit in Kruen, Germany, on Monday. AP

The leaders vowed that Russian President Vladimir Putin and those responsible would be held to account for Monday's strike in the city of Kremenchuk, carried out during the shopping mall's busiest hours.

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"Indiscriminate attacks on innocent civilians constitute a war crime," they said in a statement condemning the "abominable attack."

Ukraine accused Russia of deliberately targeting civilians, with President Volodymyr Zelensky calling it "one of the most brazen terrorist acts in European history" in his evening broadcast posted on Telegram.

Volodymyr Zelenskyy shakes hands with Emmanuel Macron before a meeting in Kyiv. File/AP

"A peaceful town, an ordinary shopping centre — women, children ordinary civilians inside," said Zelensky, who earlier shared a video of the mall engulfed in flames with dozens of rescuers and a fire truck outside.

A strike in Kharkiv, in Ukraine's northeast, killed five people and wounded 19 others, including four children, authorities said.

'Cruelty, barbarism'

British Prime Minister Boris Johnson, speaking from the G7 gathering in the Bavarian Alps, said the Kremenchuk attack demonstrated Putin's "depths of cruelty and barbarism."

US Secretary of State Antony Blinken said the world was "horrified", while UN chief Antonio Guterres's office condemned the strike as "totally deplorable".

A sign is pictured during the G7 summit at the Bavarian resort of Schloss Elmau castle, in Kruen, Germany. AP

French President Emmanuel Macron denounced the attack as an "abomination".

Diplomats said Ukraine requested a Tuesday meeting on the strikes at the UN Security Council, where Russia wields veto power but has not been able to prevent critical discussion of the invasion.

US President Joe Biden and his peers from the wealthy Group of Seven nations are seeking to tighten the economic screws on Moscow, even as soaring energy and food prices drive up global inflation.

"We will continue to provide financial, humanitarian, military and diplomatic support and stand with Ukraine for as long as it takes," the G7 said in a statement on the summit's second day.

To help bring down surging prices, France urged oil-producing nations to raise output in an "exceptional manner" and Macron backed a return to the market of crude from Iran and Venezuela, both under US sanctions.

On Sunday, the G7 announced plans to stop imports of Russian gold.

Agence France-Presse