NATO says it will significantly increase troops assigned to its eastern flank.

NATO is set to approve its biggest overhaul of its defenses since the Cold War, significantly increasing the number of troops assigned to defend the alliance’s eastern flank and making a major commitment to position heavy military equipment there.

As the Atlantic alliance’s annual summit kicks off on Tuesday evening in Madrid, global leaders are huddling across Europe at two other meetings to address the economic, humanitarian and defense fallout from the nearly five months of war in Ukraine.

President Biden and the other leaders of the Group of 7 nations hold a third day of meetings, and the United Nations coordinates grain negotiations.

At the NATO summit, which runs until Thursday, the group will approve its first updated mission statement in 12 years, which will tackle military spending and planning. The increase in troops on the eastern flank is closest to Russia and Belarus, where positioning equipment like tanks and artillery would bolster an allied response to any Russian threat or aggression.

The alliance also plans to address the dispute around the efforts by Sweden and Finland to join NATO, a move that Turkey opposes.

In the Bavarian Alps, the G7 continues to discuss the war, oil prices and how to more effectively increase economic pressure on Russia. Meanwhile, the United Nations aims to bring together Ukraine, Russia and Turkey to negotiate security guarantees allowing Ukraine to export its grain, a critical step to address world hunger.

Russian forces continued to make slow but steady gains in Ukraine’s east, imposing heavy casualties on Ukraine’s Army. And Russia has unleashed a days-long torrent of missile strikes across Ukraine. On Monday, one on a shopping mall in the country’s center killed at least 16 people.

In his nightly address on Monday, President Volodymyr Zelensky of Ukraine railed against the brutal onslaughts, which some have seen as calculated displays of brutality during a week of Western diplomacy.

“This is nothing but terror,” Mr. Zelensky said. Since the beginning of the war, he said, Russia had used almost 2,800 cruise missiles against Ukraine in addition to uncounted bombs, shells and rockets.

Mr. Zelensky urged Ukrainian civilians to take shelter when air raid alarms sound. “Don’t ignore it,” he said. “Russia will stop at nothing.”

The conflict has repeatedly threatened to broaden, most recently into Lithuania. That country has been suffering coordinated cyberattacks after placing restrictions on cargo traffic to Kaliningrad, the isolated Russian territory between Lithuania and Poland on the Baltic Sea. Lithuanian officials blamed hackers in Russia for the attacks, which have targeted both government and private organizations.