Two Russian missiles slammed into a crowded shopping centre in the central Ukrainian city of Kremenchuk on Monday, killing at least 16 people and wounding 59, officials said.

President Volodymyr Zelenskiy said more than 1,000 people were in the mall at the time of the attack, which witnesses said caused a huge fire and sent dark smoke billowing into the sky.

At least 16 people were killed and 59 injured, Ukraine's emergency services said.

A Reuters reporter saw the charred husk of a shopping complex with a caved-in roof. Firefighters and soldiers were pulling out mangled pieces of metal as they searched for survivors.

The mall was engulfed in a wall of flame which turned to thick clouds of smoke as firefighters worked to contain the blaze. Aerial photos showed the structure reduced to twisted metal, with workers combing through growing piles of rubble.

"It is impossible to even imagine the number of victims ... It's useless to hope for decency and humanity from Russia," Zelenskiy wrote on the Telegram messaging app.

Kremenchuk, an industrial city of 217,000 before Russia's Feb. 24 invasion of Ukraine, lies on the Dnipro River in the region of Poltava and is the site of Ukraine's biggest oil refinery.

Dmytro Lunin, governor of the central Poltava region, wrote on Telegram that it was too soon to talk of a final death toll as rescuers continued to trawl through the rubble.

"It's an act of terrorism against civilians," he said separately, suggesting there was no military target nearby that Russia could have been aiming at.

At one point, paramedics rushed into the building after rescuers called out "200" meaning they had found one or more bodies in the building. Reporters were later pushed away from the scene as air raid sirens wailed again.

UKRAINE WANTS MORE WEAPONS

As night began to fall, rescuers brought lights and generators to continue the search. Worried family members, some close to tears and with hands over their mouths, lined up at a hotel across the street from the mall where rescue workers had set up a base.

Kiril Zhebolovsky, 24, was looking for his friend, Ruslan, 22, who worked at an electronics store and hadn't been heard from since the blast. "We sent him messages, called, but nothing," he said. He left his name and phone number with the rescue workers in case his friend is found.

A mall worker who gave his name as Roman, 28, told Reuters that the mall's management had only three days ago allowed shops to remain open during air raid sirens.

Ukraine's air force command said the mall was hit by two long-range X-22 missiles fired from Tu-22M3 bombers that flew from Shaykovka airfield in Russia's Kaluga region.

Russia's deputy ambassador to the United Nations, Dmitry Polyanskiy, wrote on Twitter, without citing evidence, that the attack was a "Ukrainian provocation."

"Exactly what Kiev regime needs to keep focus of attention on Ukraine before (the) NATO Summit," he said, referring to the alliance's Madrid gathering due to begin on Tuesday.

NATO Secretary-General Jens Stoltenberg said on Monday that the upcoming summit will agree a new assistance package for Ukraine in areas "like secure communications, anti-drone systems, and fuel."

"We need more weapons to protect our people, we need missile defences," Andriy Yermak, head of President Zelenskiy's office, wrote on Twitter after the attack.

Vadym Denysenko, an interior ministry adviser, said Russia could have had three motives for the attack.

"The first, undoubtedly, is to sow panic, the second is to ... destroy our infrastructure, and the third is to ... raise the stakes to get the civilised West to sit down again at the table for talks," he said.

Russia, which has captured the eastern Ukrainian city of Sievierodonetsk after a weeks-long assault, has stepped up missile strikes across Ukraine in recent days.

Missiles hit an apartment block and landed close to a kindergarten in the Ukrainian capital on Sunday, killing one person and wounding several more people.