In this photo provided by the Odesa Regional Prosecutor’s Office, a damaged residential building is seen in Odesa, Ukraine, early Friday following Russian missile attacks. Ukrainian authorities said Russian missile attacks on residential buildings in the port city of Odesa have killed more than a dozen people. (Ukrainian Emergency Service via AP)

POKROVSK, Ukraine — Russian missile attacks on residential areas killed at least 21 people early Friday near the Ukrainian port of Odesa, authorities reported, a day after the withdrawal of Moscow’s forces from an island in the Black Sea seemed to ease the threat to the city.

Video of the attack before daybreak showed the charred ruins of buildings in the small town of Serhiivka, about 31 miles from Odesa. The Ukrainian president’s office said three Kh-22 missiles fired by warplanes struck an apartment building and a campsite.

Ukrainian authorities interpreted the attack as payback for Russian troops being forced from Snake Island a day earlier, though Moscow portrayed their departure as a “goodwill gesture” to help unblock exports of grain from the country.

Russian forces took control of the island in the opening days of the war in the apparent hope of using it as a staging ground for an assault on Odesa, Ukraine’s biggest port and the headquarters of its navy.

“The occupiers cannot win on the battlefield, so they resort to vile killing of civilians,” said Ivan Bakanov, head of Ukraine’s security service, the SBU. “After the enemy was dislodged from Snake Island, he decided to respond with the cynical shelling of civilian targets.”

Large numbers of civilians died in Russian airstrikes and shelling earlier in the war, including at a hospital, a theater used as a bomb shelter and a train station. Until this week, mass casualties involving residents appeared to become less frequent as Moscow concentrated on capturing eastern Ukraine’s Donbas region.

But Russian missiles struck the Kyiv region last weekend after weeks of relative calm around the capital, and an airstrike Monday on a shopping mall in the central city of Kremenchuk killed at least 19 people.

After Friday’s attack, Kremlin spokesman Dmitry Peskov reiterated that Moscow is not targeting residential areas.

Ukrainian media reported said 21 people were killed, including children. It said 38 others, including six children and a pregnant woman, were hospitalized. Most of the victims were in the apartment building, Ukrainian emergency officials said.

Oleh Zhdanov, an independent Ukrainian military analyst, said that the Russian pullback from Snake Island has “colossal psychological significance” for Ukraine.

“Snake Island is key for controlling the Black Sea and could help cover the Russian attack if the Kremlin opted for an amphibious landing operation in Odesa or elsewhere in the region,” he said. “Now those plans are pushed back.”

Ukraine’s military claimed a barrage of its artillery and missiles forced the Russians to flee the island in two small speedboats. The exact number of withdrawing troops was not disclosed.

The island took on significance early in the war as a symbol of Ukrainian defiance. When a Russian warship demanded the island’s defenders surrender, they supposedly replied: “Go (expletive) yourself.”

Zelenskyy said that although the pullout did not guarantee the Black Sea region’s safety, it would “significantly limit” Russian activities there.

“Step by step, we will push (Russia) out of our sea, our land, our sky,” he said in his nightly address.

In eastern Ukraine, Russian forces kept up their push to encircle the city of Lysychansk, the last stronghold of resistance in Luhansk, one of two provinces that make up the Donbas region.

“The shelling of the city is very intensive,” Luhansk Gov. Serhiy Haidai said. “The occupiers are destroying one house after another with heavy artillery and other weapons. Residents of Lysychansk are hiding in basements almost round the clock.”

Haidai said the Russians were fighting for control of an oil refinery on the city’s edge. But Russian Defense Ministry spokesman Igor Konashenkov said Russian and Luhansk separatist forces had taken control of the refinery as well as a mine and a gelatin factory in Lysychansk.

Ukraine’s presidential office said a series of Russian strikes in the past 24 hours also killed civilians in eastern Ukraine — four in the northeastern Kharkiv region and another four in Donetsk province.

In other developments, Zelenskyy asked Ukrainian lawmakers to fast-track the legislation needed for the country to join the European Union. His government applied for EU membership after Russia’s Feb. 24 invasion. EU leaders made Ukraine a candidate last week, acting with unusual speed and unity.

The process could take years or even decades, but Zelenskyy said in a speech to lawmakers that Ukraine can’t wait.

“Such decisions are necessary for Ukraine to advance on its path forward, and you must make them,” he said.