As a NATO member Poland could seek to invoke collective self-defence from other member countries of the alliance which was formed to counter the Russian threat.
Russia’s defence ministry denied reports that its missiles had hit Polish territory, describing them as “a deliberate provocation aimed at escalating the situation”.
“No strikes on targets near the Ukrainian-Polish state border were made by Russian means of destruction,” it said in a statement, adding the wreckage reportedly found at the scene “has nothing to do with Russian weapons”.
NATO secretary-general, Jens Stoltenberg has previously claimed its 30 members would defend and protect every inch of their territory in response to Russia’s invasion of Ukraine.
Stoltenberg said he spoke with Polish President Andrzej Duda about the explosion in the east of the country late on Tuesday.
“I offered my condolences for the loss of life,” he said on Twitter. “NATO is monitoring the situation and allies are closely consulting. Important that all facts are established.”
Ukrainian President Volodymyr Zelensky said in a statement late on Tuesday night local time that he had warned “long time ago” what would happen.
“We’ve been telling this. Terror is not limited to our national borders. It has already spread to the territory of Moldova. And today, Russian missiles hit Poland, the territory of our friendly country.
“How many times has Ukraine said that the terrorist state will not be limited to our country?”
He said a Russian missile attack on a NATO country was a strike on “collective security”.
About 100 missiles have hit areas throughout Ukraine, including at least three in the centre of the capital, Kyiv, which damaged apartment buildings and power infrastructure, causing widespread blackouts and deaths.
Russia fired three waves of missiles from the areas in or around the Caspian Sea and Black Sea. The Kyiv region was targeted for hours on Tuesday afternoon (Ukraine time) in a strike that was bigger than the October 10 attack which involved 84 missile hits.
Russia’s missile barrage follows the recent liberation of the key southern city of Kherson by Ukrainian forces and came shortly after Russian Foreign Minister Sergei Lavrov flew out of the G20 summit in Bali on a plane.
The cities of Kharkiv, Lviv, Kremenchuk and Kryvyi Rih were also hit, with large areas of the country losing power.
On Tuesday afternoon, air raid sirens were active across every region of Ukraine and authorities said there were still around 20 rockets in the air. At least one death was reported in the capital but emergency workers were still on site.
A spokesperson for the Ukrainian Air Force, Yuri Ihnat, said: “The Russians have fired around 100 missiles during this massive attack.”
“They’ve outdone the 10th of October when they fired 84 missiles.”
Power outages were confirmed in the regions of Zhytomyr, Ternopil, Lviv, Odesa, Kharkiv, Zap, Rivne, Volyn, Dnipro and Poltava.
Multiple missiles landed in the Pechersk district, in the centre of Kyiv, hitting two residential buildings. Another missile hit the Holosiyivsky district in the south of the city.
In Ukraine, the air raid sirens in Kyiv eventually stopped at 6.30pm local time with authorities telling people it was safe to come out of their bunkers. But power was still out in large areas throughout the city.
Energy Minister Herman Halushchenko said the missiles targeted power generation and transmission facilities across the country.
“This is the biggest strike on the energy system since the start of the war,” he said.
“This attack may have consequences not just for the energy systems of Ukraine, but for the energy systems of some of our neighbours.”
Videos posted online showed missiles over Kyiv being hit by Ukraine’s air defence system. Authorities later confirmed 18 missiles out of 21 were shot down over Kyiv
and at least 70 out of 90 Russian missiles were shot down throughout the country.
When the attacks started, Kyiv mayor Vitaliy Klitschko immediately took to social media platform Telegram to urge residents to get to shelters.
“Attack on the capital. According to preliminary information, two residential buildings were hit in the Pechersk district,” he said.
“Several missiles were shot down by air defence over Kyiv. Medics and rescuers at the scene of the hits. More details later.”
Two hits on power infrastructure facilities were confirmed in the Kropyvnytskyi region.
Klitschko said large parts of the city’s power needed to be shut down “to balance the energy system and prevent the equipment from being damaged”.
“The schedules of stabilising outages will not work at this time. According to preliminary data at least half of the clients in Kyiv have lost power.”
A woman in the Pechersk district of Kyiv said she was sitting with her son by the window when she heard something “humming”.
“Then I heard a ‘bang’ and then I saw another rocket which was going to the multi-storey building and I heard the explosion,” she said.
“I saw the rocket hit the third floor directly and then there’s a very big fire, and I could hear the sound going further.
Petro and Svitlana Romanchuk, aged 72 and 66, said the entrance to their building started to shake and then the windows shattered while they were lying on their bed.
“We had to crawl to the hallway and I could smell the smoke in the hallway already, and the kitchen was full of smoke,” the wife told local television channel Kyiv.
“We grabbed our clothes and ran downstairs. All our documents are in the apartment.
“We’ve heard that our neighbour died because the rocket hit directly into her balcony, we don’t know if it was the rocket or parts of it. We live in on the fourth floor and the rocket hit the third floor.
“We’ll probably spend the night at the nearby school.”
Referring to the Russians, they said :“I hope their end is near.”
In one of the buildings, emergency service workers found the dead body of a man and were still working on site as of late Tuesday afternoon.
Deputy head of the office of the president, Kyrylo Tymoshenko said “the situation in the capital is dire”.
“We’re introducing special schedules of emergency power outages,” he said.
The weather in Ukraine is starting to reach subzero temperatures, raising fears that further power outages will more significantly affect the civilian population.
Since its major defeats on the battlefield in the south and north-east of Ukraine, Russia has been increasingly targeting power infrastructure.