Nato member Poland and the head of the military alliance both say a missile strike in Polish farmland that killed two people on Tuesday (yesterday NZ time) did not appear to be an intentional attack, and that air defences in neighbouring Ukraine likely launched the Soviet-era projectile against a Russian bombardment that savaged the Ukrainian power grid.

“Ukraine’s defence was launching their missiles in various directions and it is highly probable that one of these missiles unfortunately fell on Polish territory,” said Polish President Andrzej Duda.

“There is nothing, absolutely nothing, to suggest that it was an intentional attack on Poland.”

Nato Secretary-General Jens Stoltenberg, at a meeting of the 30-nation military alliance in Brussels, echoed the preliminary Polish findings, saying: “We have no indication that this was the result of a deliberate attack.”

The initial assessments of the deadly missile landing appeared to dial back the likelihood of the strike triggering another major escalation in the nearly nine-month-old Russian invasion of Ukraine. If Russia had deliberately targeted Poland, that could have risked drawing Nato into the conflict.

Still, Stoltenberg and others laid overall but not specific blame on Russian President Vladimir Putin’s war.

“This is not Ukraine’s fault. Russia bears ultimate responsibility,” Stoltenberg said.

Before the Polish and Nato assessments, US President Joe Biden had said it was “unlikely” that Russia fired the missile but added: “I’m going to make sure we find out exactly what happened.”

Three US officials said preliminary assessments suggested it was fired by Ukrainian forces at an incoming Russian one.

That assessment and Biden’s comments at the Group of 20 summit in Indonesia contradicted earlier information from a senior US intelligence official who told The Associated Press that Russian missiles crossed into Poland.

Ukraine, once part of the Soviet Union, fields Soviet- and Russian-made weaponry, including air-defence missiles, and has also seized many more Russian weapons while beating back the Kremlin’s invasion forces.

Ukrainian air defences worked furiously against the Russian assault on Tuesday on power generation and transmission facilities, including in Ukraine’s western region that borders Poland. Ukraine’s military said 77 of the more than 90 missiles fired were brought down, along with 11 drones.

Russia said it didn’t launch the missile that landed in Poland.

A Defence Ministry spokesman said no Russian strike on Tuesday was closer than 35km from the Ukraine-Poland border. The Kremlin denounced Poland’s and other countries’ initial response and, in rare praise for a US leader, hailed Biden’s “restrained, much more professional reaction”.

US President Joe Biden, left, and British Prime Minister Rishi Sunak attend an emergency meeting of leaders at the G20 summit in Nusa Dua, Indonesia, after a missile landed in Poland near the Ukrainian border yesterday. Photo / AP

“We have witnessed another hysterical, frenzied, Russo-phobic reaction that was not based on any real data,” Kremlin spokesman Dmitry Peskov said.

Still, Ukraine was under countrywide Russian bombardment on Tuesday by barrages of cruise missiles and exploding drones, which clouded the initial picture of what exactly happened in Poland and why.

The Polish president said the projectile was “most probably” a Russian-made S-300 missile dating from the Soviet era.

“It was a huge blast, the sound was terrifying,” said Ewa Byra, the primary school director in the eastern village of Przewodow, where the missile struck. She said she knew both men who were killed — one was the husband of a school employee, the other the father of a former pupil.

Another resident, 24-year-old Kinga Kancir, said the men worked at a grain-drying facility, one as a guard, the other driving tractors.

“It is very hard to accept,” she said. “Nothing was going on and, all of a sudden, there is a world sensation.”

Ukraine said it wants immediate access to the site. Oleksiy Danilov, head of Ukraine’s National Security and Defence Council, advocated on Twitter for a “joint examination of the incident”.

In Europe, Nato members Germany and the UK laced calls for a thorough investigation with criticism of Moscow.

“This wouldn’t have happened without the Russian war against Ukraine, without the missiles that are now being fired at Ukrainian infrastructure intensively and on a large scale,” said German Chancellor Olaf Scholz.

UK Prime Minister Rishi Sunak said: “This is the cruel and unrelenting reality of Putin’s war.”

Nato Secretary-General Jens Stoltenberg during a press conference at the Nato headquarters, in Brussels overnight NZ time. Ambassadors from the 30 Nato nations gathered for emergency talks after Poland said a Russian-made missile fell on its territory, killing two people, and US President Joe Biden and his allies promised support for the investigation into the incident. Photo / AP

Ukrainian President Volodymyr Zelenskyy called it “a very significant escalation”. On the other end of the spectrum, China called for calm and restraint.

Damage in Ukraine from the aerial assault was extensive and swaths of the country were without power. Zelenskyy said about 10 million people lost electricity but tweeted overnight that 8 million were subsequently reconnected, and repair crews were labouring through the night. Previous Russian strikes had already destroyed an estimated 40 per cent of the country’s energy infrastructure.

Ukraine said the bombardment was the largest on its power grid so far. Pope Francis said it caused him “great pain and concern”.

A Washington-based think thank, the Institute for the Study of War, said Ukraine’s downing of so many Russian missiles Tuesday “illustrates the improvement in Ukrainian air defences in the last month,” which are being bolstered with Western-supplied systems.

Sweden said on Wednesday an air defence system with ammunition would form part of its latest and largest package of military and humanitarian aid to Ukraine, worth $360 million.

The US has been Ukraine’s largest supporter, providing $18.6 billion in weapons and equipment. US Defence Secretary Lloyd Austin said flows of US weapons and assistance would continue “throughout the winter so that Ukraine can continue to consolidate gains and seize the initiative on the battlefield”.

Russian attacks on Tuesday killed at least six civilians and wounded another 17, said a senior official, Kyrylo Tymoshenko. In the Kyiv region, a missile strike killed a 69-year-old woman visiting her husband’s grave at a cemetery, the regional police chief said. In central Kyiv, a woman was killed in one of two residential buildings that were damaged, the mayor said.

The Russian bombardment followed days of euphoria in Ukraine sparked by one of its biggest military successes — the retaking last week of the southern city of Kherson.

It also affected neighboring Moldova. It reported massive power outages after the strikes in Ukraine disconnected a power line to the small nation.

With its battlefield losses mounting, Russia has 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. - VASILISA STEPANENKO, AP