President Biden sought to reassure Warsaw of Washington’s commitment to NATO and the security of its allies bordering Russia on Saturday, the last day of his trip to Europe.

In a meeting with Polish President Andrzej Duda, Biden said the United States regards NATO’s Article 5 providing the alliance’s defense umbrella as a “sacred commitment.” He also convened with Ukraine’s foreign and defense ministers and visited some of the 2 million refugees who have fled to Poland. Biden is expected to wrap up his visit with a speech focused on defending democratic principles.

Biden’s trip, aimed at bolstering the NATO response to the Russian invasion, came as fierce fighting continued in Ukraine. Speaking by video to the Doha Forum in Qatar on Saturday, Ukrainian President Volodymyr Zelensky called on exporters of oil and natural gas to help “stabilize the situation in Europe” by increasing production. He also described the destruction in the port city of Mariupol, comparing it to “what we all saw in Aleppo” — a reference to the northern Syrian city battered by Syrian and Russian forces during the civil war in Syria.

Here’s what to know

  • The Pentagon said Friday that Russia has halted ground operations aimed at Kyiv and is instead focusing attacks on the eastern Donbas region. The move is seen as a sign that Moscow might be paring back its ambitions for the invasion, but air attacks on Ukraine continue.
  • For weeks, the Ukrainian city of Chernihiv north of the capital has been under near-constant Russian attack, almost entirely cut off from power, water, food and gas amid constant artillery fire. One resident has shared with The Washington Post the daily struggles that he and others face.
  • Hospitals, ambulances, doctors and patients continue to come under fire in Ukraine, with the World Health Organization documenting more than 70 such attacks since Russia invaded on Feb. 24.
  • The United Nations said it has seen evidence of mass graves in the blockaded city of Mariupol. The Washington Post has spoken with terrified residents who survived what Ukrainian officials said was a Russian airstrike on a Mariupol theater where civilians had sought shelter.
  • American teacher Tyler Jacob has been released from Russian custody and reunited with his wife and daughter. He was detained 10 days ago at a checkpoint in Crimea as he was seeking evacuation to Turkey.