KYIV — Russia and Ukraine exchanged hundreds of prisoners Sunday in what officials described as the final phase of a major three-day swap — a rare act of cooperation between the two sides amid relentless fighting and failed attempts to negotiate a ceasefire.

The exchange, which saw each country return 303 prisoners, followed the release of 307 on Saturday and 390 on Friday, making it the largest prisoner swap of the war.

The agreement was brokered during recent face-to-face peace talks in Istanbul and marks the only tangible outcome from those discussions.

Just hours before the exchange, Ukraine was hit by what officials called the largest aerial assault since February 2022.

Ukrainian Air Force spokesman Yuriy Ihnat said Russian forces launched 367 aerial weapons in a single wave, including 69 missiles and 298 drones — many of them Iranian-designed Shahed drones.

The attacks targeted more than 30 cities and regions, including Kyiv, Zhytomyr, Khmelnytskyi, Ternopil, Sumy, Odesa, Dnipro, Mykolaiv, and Kharkiv.

At least 12 people were killed and dozens injured across the country. In Kyiv alone, four deaths and 16 injuries were reported, including damage to a student dormitory and private homes.

President Volodymyr Zelenskyy condemned the attacks as deliberate strikes on civilian areas and used the occasion to renew his appeal for stricter Western sanctions on Russia. “Without truly strong pressure on the Russian leadership, this brutality cannot be stopped,” he said. “Sanctions will certainly help.”

The aerial barrage coincided with Kyiv Day, a national holiday marking the city’s founding in the 5th century, turning a normally celebratory occasion into one of mourning.

Ukrainian Foreign Minister Andrii Sybiha called it a “sleepless night,” while emergency services scrambled to contain fires and search for victims in the rubble.

In the Zhytomyr region, three children aged 8, 12, and 17 were killed. Another four fatalities were reported in Khmelnytskyi and one in Mykolaiv.

Rescue workers and residents described scenes of devastation in towns such as Markhalivka, just outside Kyiv, where multiple homes were destroyed.

Despite the violence, Ukraine confirmed the return of 303 of its defenders, with Zelenskyy stating that the soldiers belonged to the Armed Forces, National Guard, Border Guard, and Special Transport Service. Russia also confirmed the return of its troops.

The prisoner exchanges have brought home civilians and combatants alike, offering brief moments of relief in a war that has dragged on for more than three years. Still, the front lines remain active, with Russian officials claiming gains in Ukraine’s Sumy and Kharkiv regions.

Russian Defense Ministry sources said troops from its "North" group had pushed Ukrainian forces back from areas near the Kursk border, claiming the capture of several towns over the past week. Kyiv has not confirmed these claims.

While the scale of the latest prisoner exchange was unprecedented, it has not led to a broader de-escalation. — Agencies