Two people were killed after stray Russian missiles inadvertently hit a small Polish village near the border with Ukraine.

A senior US intelligence official confirmed Russian missiles had crossed into Nato member Poland, killing two people.

Polish government spokesman Piotr Mueller did not immediately confirm the information, but said Prime Minister Mateusz Morawiecki has gathered the Committee of the Council of Ministers for National Security and Defence Affairs to hold an emergency meeting due to a “crisis situation”.

Polish media reported that two people died on Tuesday afternoon after a projectile or projectiles struck an area where grain was drying in Przewodów, a Polish village near the border with Ukraine.

Polish Radio ZET claimed two stray missiles hit Polish soil, without providing more details.

The blasts came as Moscow launched fresh missile attacks across Ukraine, the heaviest wave of missile strikes in nearly nine months of war.

Russian airstrikes targeting energy and other facilities rocked Ukraine from east to west, causing broad power blackouts. A senior official warned that the situation was “critical” and urged Ukrainians to “hang in there” as neighbourhoods went dark.

The aerial assault, which killed at least one person in a residential building in the capital, Kyiv, followed days of euphoria in Ukraine sparked by one of its biggest military successes in the nearly nine-month war — the retaking last week of the southern city of Kherson.

At least a dozen regions reported strikes, which caused multiple blackouts.

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Ukrainian State Emergency Service firefighters work to extinguish a fire at the scene of a Russian shelling in Kyiv. Photo / Andrew Kravchenko, AP

A Ukrainian air force spokesman said Russia fired around 100 missiles. President Volodymyr Zelenskyy put the number at 85.

Zelenskyy warned that more attacks may be coming but defiantly vowed, with a shake of his fist: “We will survive everything”.

A senior official, Kyrylo Tymoshenko, said the barrage was “another planned attack on energy infrastructure facilities”.

“Most of the hits were recorded in the centre and in the north of the country. In the capital, the situation is very difficult,” Tymoshenko wrote on Telegram.

It was difficult elsewhere, too.

As its battlefield losses mount, Russia has in recent months increasingly resorted to targeting Ukraine’s power grid, seemingly hoping to turn the approach of winter into a weapon by leaving people in the cold and dark.

Windows of an apartment building are illuminated during a blackout in central Kyiv. Photo / Andrew Kravchenko, AP

While city after city reported attacks, Tymoshenko appealed to Ukrainians to hang on and acknowledged the severity of the situation.

Among regions where officials reported strikes were Lviv, Zhytomyr, Khmelnytskyi and Rivne in the west, and Kharkiv, Ukraine’s second-largest city in the northeast. Several missile strikes also hit Kryvyi Rih, Zelenskyy’s native city, according to its mayor, Oleksandr Vilkul.

In Kyiv, mayor Vitali Klitschko said authorities found a body in one of three residential buildings that were struck in the capital, where emergency blackouts were also announced by power provider DTEK.

Video published by a presidential aide showed a five-storey, apparently residential building in Kyiv on fire, with flames licking through apartments. Klitschko said air defence units also shot down some missiles.

Ukraine had seen a period of comparative calm since previous waves of drone and missile attacks several weeks ago.

Authorities were already working furiously to get Kherson back on its feet and beginning to investigate alleged Russian abuses there and its surrounds.

Two Ukrainian defence forces members stand next to a sign reading 'Kherson region' in southern Ukraine, Photo / Bernat Armangue, AP

The southern city is without power and water, and the head of the UN human rights office’s monitoring mission in Ukraine, Matilda Bogner, decried a “dire humanitarian situation” there.

Speaking from Kyiv, Bogner said her teams were looking to travel to Kherson to try to verify allegations of nearly 80 enforced disappearances and arbitrary detention they have turned up in the area and “understand whether the scale is in fact larger than what we have documented already”.

The head of the National Police of Ukraine, Igor Klymenko, said authorities are to start investigating reports from Kherson residents that Russian forces set up at least three alleged torture sites in now-liberated parts of the wider Kherson region and that “our people may have been detained and tortured there”.

“Mine clearance is under way. After that, I think, today, investigative actions will begin,” he said on Ukrainian TV.

The retaking of Kherson was one of Ukraine’s biggest successes in the nearly nine-month Russian invasion and dealt another stinging blow to the Kremlin. But large parts of eastern and southern Ukraine remain under Russian control and fighting continues.

Zelenskyy on Tuesday likened the recapture of the Kherson to the Allied landings in France on D-Day in World War II, saying both were watersheds on the road to eventual victory.

Residents receive food donations in Novokyivka, southern Ukraine. Photo / Bernat Armangue, AP

“It’s like, for example, D-Day — the landing of the Allies in Normandy. It was not yet a final point in the fight against evil, but it already determined the entire further course of events. This is exactly what we are feeling now,” he said in a video address to the Group of 20 (Gop20) summit in Indonesia.

The liberation of Kherson — the only provincial capital that Moscow had seized — had sparked days of celebration in Ukraine and allowed families to be reunited for the first time in months. But as winter approaches, the city’s remaining 80,000 residents are without heat, water or electricity, and short on food and medicine.

Still, US President Joe Biden called it a “significant victory” for Ukraine. Speaking on the sidelines of the Gop20 summit, Biden added: “We’re going to continue to provide the capability for the Ukrainian people to defend themselves”.

Zelenskyy warned of possible more grim news ahead.

“Everywhere, when we liberate our land, we see one thing — Russia leaves behind torture chambers and mass burials. How many mass graves are there in the territory that still remains under the control of Russia?” Zelenskyy asked.

- John Leicester, AP