Poland put its military on heightened readiness Tuesday after Russian missiles reportedly landed inside the NATO member's borders in a potentially major escalation of the war in Ukraine.
Ukraine's President Volodymyr Zelensky accused Russia of firing the missiles into Poland, but there was no immediate confirmation from either Warsaw or Washington, and Moscow dismissed the reported strikes as a "provocation" intended to escalate tensions.
The strikes, which allegedly killed two people, drew widespread condemnation, with European Union chief Charles Michel saying he was "shocked" and French President Emmanuel Macron calling for talks at the G20 summit underway in Indonesia.
Warsaw put its military on heightened alert after an emergency national security council meeting.
"There has been a decision to raise the state of readiness of some combat units and other uniformed services," spokesman Piotr Muller told reporters after the meeting in Warsaw.
The US State Department said Washington "will determine what happened and what appropriate next steps would be."
Poland is protected by NATO's commitment to collective defence — enshrined in Article 5 of its founding treaty — but even if a cross-border strike is confirmed, the alliance's response would likely be heavily influenced by whether it was accidental or intentional.
"Today Russian missiles hit Poland, the territory of an allied country. People died", Zelensky said in an address to the nation, describing the alleged strikes as "a very significant escalation."
Ukraine's Foreign Minister Dmytro Kuleba tweeted to call for NATO members to convene an "immediate" summit.
Hungary, also a NATO member which borders Ukraine, convened its national defence council in response to the reports, a spokesman for Prime Minister Viktor Orban said.
The reports came after Russian missile strikes hit cities across Ukraine Tuesday — including Lviv near the border with Poland — which Kyiv said cut power to seven million homes.
Zelensky said Russia had fired 85 missiles at energy facilities across the country, condemning the strikes as an "act of genocide" and a "cynical slap in the face" of the G20 as world leaders gathered for a summit expected to tackle the war in Ukraine.
Moldova, which also borders Ukraine, reported power cuts because of the missiles fired at its neighbour and called on Moscow to "stop the destruction now".
'Now is the time'
On Monday, Zelensky made a surprise visit to Kherson, announcing that Ukraine's recapture of the key southern city marked "the beginning of the end of the war".
He told the G20 summit in Bali on Tuesday that "now is the time" to end the war, while Washington said the Russian strikes in Ukraine would "deepen the concerns among the G20 about the destabilising impact of Putin's war".
White House National Security Adviser Jake Sullivan said Russia was again trying to destroy Ukrainian critical infrastructure.
Since September, Ukraine forces have been pushing deeper into the south. Russia announced last week a full withdrawal from the regional capital of the southern Kherson region, allowing Ukraine's forces to re-enter the city.
Tuesday's missile strikes came after Russia-appointed officials in Nova Kakhovka said they were leaving the important southern city, blaming artillery fire from Kyiv's forces.
They also claimed "thousands of residents" had followed their recommendation to leave to "save themselves", saying Kyiv's forces would seek "revenge on collaborators".
Key dam at risk
Nova Kakhovka sits on the eastern bank of the Dnipro River, now a natural dividing line between Ukraine's forces that retook Kherson city on the west side and Russia's forces on the opposing bank.
It is also home to the Kakhovka hydroelectric dam which was captured in the beginning of the invasion because of its strategic importance supplying the Moscow-annexed Crimean peninsula.
The Russian-controlled dam is a particular focus now after Zelensky accused Russian troops of planning to blow it up to trigger a devastating flood.
Any defects at the dam would cause water supply problems for Crimea, which has been under Russian control since 2014 and which Ukraine hopes to recapture.
Russian forces said last week that a Ukrainian strike had damaged the dam.
The Russian-appointed head of the occupied part of the Kherson region, Vladimir Saldo, said Tuesday the dam was no longer operating.
"The situation is more dangerous — not with electricity generation — but with the dam itself, which, in the event of an explosion, would flood a fairly large area," he said on state-run television channel Rossiya-24, according to Russian agencies.
The loss of Kherson was the latest in a string of setbacks for the Kremlin, which invaded Ukraine on February 24 hoping for a lightning takeover that would topple the government in days.