(NewsNation) — Several rockets struck the western Ukrainian city of Lviv on Saturday in what officials say were two separate attacks that occurred the same day President Joe Biden visited the capital of Poland, whose border is just 45 miles away.

The powerful explosions frightened a city that had been a haven for hundreds of thousands of people fleeing the Russian assault on other parts of Ukraine.

Maxym Kozytsky, the regional governor, said on Facebook that preliminary indications were five people were injured in the first attack but did not specify what the two rockets hit. Hours later, he reported three more explosions outside the city, again with no details.

Lviv Mayor Andriy Sadovyi called the second round of explosions a rocket attack, saying it did significant damage to an unspecified “infrastructure object.”

Lviv had been largely spared since Russia’s Feb. 24 invasion of Ukraine, although missiles struck an aircraft repair facility near the international airport a week ago.

The back-to-back attacks on Saturday brought a chill to residents and displaced Ukrainians who had seen Lviv as a relatively safe place to rebuild their lives. Home to about 700,000 people before the invasion, the city has absorbed many more.

Kozytskyy said a man was detained on suspicion of espionage at the site of one of the two rocket attacks that rattled the city on Saturday.

He said police found the man had recorded a rocket flying toward the target and striking it. Police also found on his telephone photos of checkpoints in the region, which Kozytskyy said had been sent to two Russian telephone numbers.

Rockets hit an oil storage facility and an unspecified industrial facility, wounding at least five people. A thick plume of smoke and towering flames could be seen on Lviv’s outskirts hours after the attacks.

Biden ended his trip to Europe in Poland with a hit at Russian President Vladimir Putin, telling people gathered at the Royal Castle in Warsaw that “For God’s sake, this man cannot remain in power.”

During his speech, Biden touted Western sanctions against Russia and evoked historical figures such as Abraham Lincoln and the late Madeleine Albright. Using the words of Pope John Paul, he said “Be not afraid.”

Biden rebuked Putin multiple times in his speech, calling the Russian President a tyrant who has the “audacity, like all our autocrats before him,” to think might makes right.

Despite his harsh words for Putin, Biden stressed that the Russian people “are not our enemy.”

“This is not who you are,” he said.

The war, Biden warned, will not be won in days, or months. Instead, Europe needs to steel itself for the long haul ahead, he said.

Saturday marks the 31st day since the Russian invasion of Ukraine started.

Russian forces have entered a city north of Kyiv, Slavutych, and seized a hospital there, the governor of the Kyiv region said.

Slavutych is outside the exclusion zone that was established around the Chernobyl nuclear power plant after the 1986 disaster.

Russian forces in Ukraine have seemingly shifted their focus from the country’s capital, Kyiv, to prioritizing the contested Donbas region in the country’s industrial east, officials said Friday.

This could mean a new phase of war, although it is still too early to know where this will lead.

Dug-in defensive positions recently taken by some Russian forces near Kyiv indicate recognition of Ukrainian resistance, but Russian forces might also be aiming to continue the war with a narrower focus, using Donbas as a new starting point.

Ukrainian President Volodymyr Zelenskyy, in his nightly address Friday, noted that Russian forces have lost thousands of troops but still haven’t been able to take Kyiv or Kharkiv, the second-largest city.

He appealed again to Russia for an end to the war but still said Ukraine would not agree to give up any of its territory for the sake of peace.

As the Russia-Ukraine War that started last month rages, a vast apparatus is being built to gather and preserve evidence of potential war crimes. While the United States declared Russian forces are violating international laws of war stemming from World War II, it remains unclear who will be held accountable and how.

These possible war crimes in Ukraine include destroying homes, firing on civilians as they evacuate through safe corridors, targeting hospitals, using indiscriminate weapons like cluster bombs in civilian areas, attacking nuclear power plants and intentionally blocking access to humanitarian aid or food and water.

The Associated Press has independently documented at least 34 assaults on Ukrainian medical facilities by Russian forces.

In addition to war crimes, Russia is now accused of forcibly taking thousands of Ukrainians to Russia. According to one Ukraine official, as many as 402,000 people, including 84,000 children, have been taken “hostage.”

Air raid sirens sounded Saturday in Lviv, and the governor of the region, Maxym Kozytsky, reported “three powerful explosions” near the Western city, without giving details on what was hit.

Biden and Polish President Andrzej Duda gathered Saturday to speak about their shared effort to end the war. The U.S. president told his Ukrainian counterpart that “your freedom is ours,” echoing one of Poland’s unofficial mottos and assuring Duda that the U.S. and other NATO allies would come to their aid should Russia attack.

Biden, after meeting with Ukrainian refugees in Poland, called Putin a “butcher.” As he listened to the refugees’ stories, he held their hands and picked up a young Ukrainian girl in a pink coat, telling her she reminded him of his own granddaughters.

“What I am always surprised by is the depth and strength of the human spirit,” Biden told reporters after his conversations. “Each one of those children said something to the effect of ‘Say a prayer for my dad or grandfather or my brother.’”

Some 3.5 million Ukrainians have fled the country, half of them children, according to the European Union. More than 2 million have gone to Poland.

This week, Biden announced $1 billion in additional aid and said the U.S. would accept up to 100,000 refugees.

In Chernihiv, the situation has gotten dire. Residents spend nights huddling underground from Russian strikes, and daylight hours are devoted to hunting down food and water or standing in line for what little food’s available as shells and bombs rain down in the city.

“In basements at night, everyone is talking about one thing: Chernihiv becoming (the) next Mariupol,” said 38-year-old resident Ihar Kazmerchak, a linguistics scholar.

The southern Ukrainian city of Mariupol has become the site of some of the worst suffering the war has seen, with corpses lying in the street and people fighting over scarce food, as well as melting snow for drinking water.

Chernihiv Mayor Vladyslav Atroshenko has said that more than half of the city’s 280,000 residents fled amid the unrelenting attacks.

The city’s hospitals are no longer operating, and residents cook over open fires in the street because they have no power.

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