Russia hits Ukraine with over 40 missiles, including in areas that were recently spared.

UZHGOROD, Ukraine — As intense battles raged in eastern Ukraine and Russian forces pressed to cut off the supply lines for thousands of Ukrainian soldiers, Moscow unleashed more than 40 missiles on targets across the country on Saturday morning, including in areas in the north and west that have been largely spared in recent weeks.

The barrage, which officials say was fired from Belarusian airspace and which appeared to hit mostly military installations, was a stark reminder of the vulnerability of cities across Ukraine. It also spotlighted the escalation in Russian air attacks in recent weeks.

Even in western and northern regions where the wail of air alarms had become more sporadic in recent weeks, they rang out five times in less than 48 hours to signal that missiles had been fired within striking distance, a noticeable uptick in intensity.

Dozens of the missile strikes were launched by Russian aircraft in Belarusian airspace overnight, according to a Belarusian monitoring group, Belarusian Guyun, that has been detailing Russian actions since the start of the war.

The strikes came hours before President Vladimir V. Putin of Russia was scheduled to meet with President Aleksandr G. Lukashenko of Belarus in St. Petersburg. Belarusian forces are also once again conducting military drills near the border with the Kyiv region, raising tension and putting Ukrainian authorities on high alert.

Ukraine’s military intelligence agency called the Russian assault “a large-scale provocation of Russia for the purpose of further dragging Belarus into the war against Ukraine.” While many Western military analysts say it is unlikely that Belarus would directly join the Russian war effort, Mr. Lukashenko’s hold on power is dependent on the Kremlin’s support.

According to the Belarusian monitoring group, the bombers took off from Russian airfield, entered Belarusian airspace, flew up to the border with Ukraine, and fired missiles.

Those details were confirmed by the local authorities in Ukraine. At least 24 missiles fired from Belarus hit the outskirts of Zhytomyr, a city about 80 miles west of Kyiv, the mayor of Zhytomyr, Sergey Sukhomlyn, said on Saturday.

The toll from overnight strikes across the country was not immediately clear, and the Ukrainians often do not release details about strikes on military installations. But Vitaly Bunechko, the governor of the Zhytomyr region, said that at least one soldier had been killed and that another had been wounded.

In the Chernihiv region directly east of Kyiv, Vyacheslav Chaus, the area’s governor, said that a “massive missile strike” from Belarusian territory had destroyed infrastructure in the village of Desna, where Ukrainian forces also have a military installation.

“Rockets were also roaring over Chernihiv today,” he said on Saturday. “This indicates that the war in Chernihiv region is not over.”

Chernihiv was besieged early in the war by Russian forces, who killed and wounded a number of civilians in attacks in March but never took the city. Ukrainian troops forced the Russian fighters from the area in early April.

In another salvo that the Ukrainians said was launched by Russian forces on the Black Sea on Saturday morning, four missiles hit a “military object” in the Yavoriv area, the site of a military training base in Lviv region. Four people were injured and were taken to a hospital, according to Maksym Kozytskyi, the region’s governor.

The Yavoriv district has been targeted several times since the start of the war, including a major attack in March that killed and injured dozens.

Megan Specia reported from Uzhgorod, Ukraine, and Marc Santora from Warsaw.