Video of the scene shows a fireball engulfing the shopping center in Kremenchuk, eastern Ukraine, as people flee for their lives.

Ukrainian President Volodymyr Zelensky said as many as 1,000 people were in the mall at the time.

At least two people have been killed and dozens injured. The death toll could still rise.

Local mayor Vitaliy Meletskiy said the mall was “very busy”.

“The occupiers have hit a shopping center with more than a thousand civilians in it,” Zelensky said on Telegram.

“It is on fire and rescuers are trying to put out the fire, the number of victims is unimaginable.

“It posed no threat to the Russian military. No strategic value. People just wanted to live normal lives, and that’s what makes the occupiers so angry.

“Out of helplessness, Russia continues to hit ordinary people. It is vain to expect it to be reasonable or humane.”

A video shared by Zelensky showed the mall engulfed in flames with dozens of rescuers and a fire truck outside.

Ukrainian president’s deputy chief of staff Kyrylo Tymoshenko said on Telegram that about 20 have been injured so far, nine of them in “serious condition”.

US Secretary of State Antony Blinken said: “The world is shocked by Russia’s missile strike today.”

UN spokesman Stephane Dujarric described the attack as “deplorable”.

“Any civilian infrastructure, including, of course, shopping malls, and civilians should never be targeted,” he said.

British Prime Minister Boris Johnson repelled the attack. “This horrific attack has shown once again the depths to which cruelty and barbarity will sink the Russian leader.

“Once again, our thoughts are with the families of innocent victims in Ukraine.”

Dmytro Lunin, Ukraine’s Poltava region regional head, described the attack as a “war crime”.

“The missile attack on a shopping center with people in Kremenchuk is another Russian war crime. A crime against humanity. This is an overt and cynical act of terror against the civilian population.”

NATO troops ready

The attack came just hours after NATO announced it would increase its preparedness forces to “well over 300,000”.

Leaders of the US-led military alliance are set to gather in Madrid this week for what NATO chief Jens Stoltenberg said would be a “transformative” summit as it grapples with the fallout from the Moscow invasion of its pro-Western neighbor.

Stoltenberg said allies would bolster some of their battlegroup formations along NATO’s eastern flank “to the brigade level” — tactical units of some 3,000-5,000 troops — and boost readiness levels to “well over 300,000.”

In addition, heavier weapons, including air defense systems, would be pushed forward and troops would be pre-allocated to defend specific NATO members on the alliance’s exposed eastern edge.

“This is the largest overhaul of our collective defense and deterrence since the Cold War,” Stoltenberg said.

He gave no further details about the extra high-level preparedness forces or how they might be deployed by the alliance.

NATO currently has a high-preparedness force of approximately 40,000 troops under its command.

The more than 300,000 troops are expected to form a larger pool that the alliance can tap into in the event of an emergency.

Stoltenberg also said the leaders would agree to bolster NATO’s vital support to a war-torn Ukraine.

That package would include “substantial supplies” of equipment such as secure communications, anti-drone systems and fuel, and in the longer term help Ukraine transition to using more advanced NATO-standard weapons.

This support is separate from any weapons NATO members — led by the United States — are already sending to Ukraine, including anti-tank missiles, artillery and air defenses to help Russia stop Russia’s attack.

NATO has built up its armed forces in the east of the alliance since Moscow first invaded Ukraine with the annexation of Crimea in 2014.

The alliance has sent tens of thousands of additional troops to the region since Moscow launched its large-scale invasion on February 24.

NATO now has eight battlegroups spread across its eastern members, and Stoltenberg said some of these – likely in the Baltics and Poland – would be bolstered to “brigade level”.

Nervous leaders in the Baltic states have pushed for large and permanent troop deployments that could halt Kremlin forces on the NATO border.

Germany has said it would take charge of a new brigade in Lithuania – where it already has troops – but most of those troops would be permanently stationed in their home countries