U.S. President Joe Biden said it was unlikely that a missile that struck Poland on Tuesday was fired from Russia, adding: "I'm going to make sure we figure out exactly what happened."
Biden, who is in Bali, Indonesia, for a meeting of the Group of 20 largest economies, came from an emergency meeting where he hosted the leaders of Canada, France, Germany, Italy, Japan, the United Kingdom and the European Union, along with the president of the European Council and the prime ministers of NATO allies Spain and the Netherlands.
Earlier Biden spoke to Polish President Andrzej Duda and NATO Secretary-General Jens Stoltenberg.
The United States and Western allies are investigating the reports Tuesday that a blast in NATO member Poland resulted from stray Russian missiles, while Russia's defense ministry denies any connection to the blast.
"We are aware of the press reports alleging that two Russian missiles have struck a location inside Poland on the Ukrainian border. I can tell you that we don't have any information at this time to corroborate those reports and are looking into this further," Pentagon press secretary Brig. Gen. Pat Ryder told reporters at the Pentagon.
Stoltenberg said via Twitter that he also had spoken with Duda about the explosion and offered his condolences for the loss of life. Reports say at least two Polish citizens were killed.
"NATO is monitoring the situation, and Allies are closely consulting. Important that all facts are established," Stoltenberg said.
Eliot Higgins, the founder of the investigative journalism and open-source intelligence group Bellingcat, reposted a social media image of the debris from the alleged site in Poland and noted that it appeared to be from an air defense missile, like the S-300s used by Ukraine to shoot down Russian missiles. If confirmed, this could mean the blast potentially originated from a Ukrainian intercept of a Russian missile targeting Ukrainian territory.
Asked what the incident could mean for the administration, Ryder declined to discuss hypotheticals, adding, "When it comes to our security commitments and Article Five, we've been crystal clear that we will defend every inch of NATO territory."
Secretary of Defense Lloyd Austin and Chairman of the Joint Chiefs of Staff Gen. Mark Milley are to host the Ukrainian Defense Contact Group meeting virtually at the Pentagon on Wednesday. Ryder said Ukraine would provide a battlefield assessment, which would lead to a "robust discussion on Ukraine's security needs."
Russia launched waves of airstrikes on Ukraine Tuesday, targeting 10 regions, including the capital of Kyiv, in a military rebuke to Ukrainians reveling in one of their biggest wartime successes, last week's takeover of the key southern city of Kherson.
The airstrikes rocked Ukraine from east to west, hitting energy facilities and other infrastructure, as well as residential buildings in Kyiv, where one death was reported.
A video in Kyiv, published by a presidential aide, showed a five-story building, apparently a residential structure, on fire. Mayor Vitali Klitschko said three residential buildings were hit but that air defense units shot down other missiles.
Air raid alerts sounded throughout the country. The barrage of nearly 100 strikes — including with missiles — followed days of euphoria in Ukraine after the Russian retreat from Kherson and the Ukrainian takeover of the regional capital that Moscow's forces had captured early in the nearly nine-month war.
In Bali, Indonesia, at the meeting of the leaders of the Group of 20 largest industrialized countries, White House national security adviser Jake Sullivan condemned the Russian airstrikes.
"It is not lost on us that, as world leaders meet at the G-20 in Bali to discuss the issues of significant importance to the lives and livelihoods of people around the world, Russia again threatens those lives and destroys Ukraine's critical infrastructure. These Russian strikes will serve to only deepen the concerns among the G20 about the destabilizing impact of (Russian President Vladimir) Putin's war," Sullivan said in a statement. "We will stand with Ukraine for as long as it takes."
With its battlefield defeats, Russia has resorted to more long-range aerial attacks on Ukraine's power grid as winter approaches, believing it to be a demoralizing psychological weapon to leave Ukrainians in the cold and dark.
Ukrainian officials reported strikes Tuesday in Lviv, Zhytomyr, Khmelnytskyi and Rivne in the west, and Kharkiv, Ukraine's second-largest city, in the northeast. Several missiles also hit Kryvyi Rih, President Volodymyr Zelenskyy's native city, according to Oleksandr Vilkul, head of the military administration in Kryvyi Rih.
Ukrainian officials were working frantically to restore water and power in Kherson and begin to investigate alleged Russian abuses there and in surrounding communities.
Matilda Bogner, the head of the United Nations human rights office's monitoring mission in Ukraine, on Tuesday decried a "dire humanitarian situation" in Kherson. She said her teams are trying to verify allegations of nearly 80 cases of enforced disappearances and arbitrary detention and "understand whether the scale is in fact larger than what we have documented already."
Zelenskyy on Tuesday said a "real and complete cessation of hostilities" will result if Russia withdraws all its troops from Ukraine and restores Ukrainian control to his country's territory along the border with Russia.
Speaking virtually to the world leaders at the G-20 summit, Zelenskyy said delays in bringing an end to the conflict mean the deaths of more Ukrainians and more threats to the world.
"I am convinced now is the time when the Russian destructive war must and can be stopped," Zelenskyy said.
White House correspondent Anita Powell contributed to this report. Some information in this report came from The Associated Press.