KYIV — Ukrainian authorities say Russian missiles have struck a multi-story block of flats and two other civilian facilities in Ukraine's southern Odesa region, killing at least 18 people and wounding dozens.

One missile struck the building in the village of Serhiivka in the Bilhorod-Dnistrovskyi district — which lies about 80 kilometres south of the city of Odesa — at about 0100 local time (midnight CET), killing 16 people, Odesa region emergency official Ihor Budalenko told local television.

He added that 41 people had been rescued from the building where 152 lived, and rescue work was ongoing to find people who could still be trapped.

Ukrainian news reports said the target of the missile attack was a multi-story apartment building and a recreational area. Video of the pre-dawn attack showed the charred remains of buildings.

Serhiy Bratchuk, spokesman for the Odesa regional administration, said "a nine-story residential building" was hit, as well as two holiday camps nearby.

Odesa region governor Maksym Marchenko said in a post on Telegram that the death toll stood at 18, with another 31 in hospital. He said Russia had used Soviet-era Kh-22 missiles, which all came from the direction of the Black Sea.

The deputy head of the Ukrainian presidential office, Kirill Tymoshenko, also said 18 people died, including two children.

Earlier, Ukraine's emergency services said the missile which struck the apartment block also caused a fire in an attached store building. Rescue workers said the second missile hit two other buildings nearby, killing "three people, including a child".

The Ukrainian claims could not be immediately verified.

A Ukrainian military leader said on Thursday that the number of Russian missile strikes on Ukraine had more than doubled in the last two weeks. Brigadier General Oleksii Hromov estimated that 68 civilian sites had been hit, and claimed that Moscow was using inaccurate Soviet-era missiles for more than half of the attacks.

Russia, which launched its full-scale invasion of Ukraine on February 24, denies targeting civilians and says it hits only military infrastructure.

The latest attacks come a day after Russia pulled its troops out of the strategically important Snake Island in the Black Sea in what the defence ministry in Moscow described as a "goodwill gesture" aimed at easing grain exports from Ukraine.

The Ukrainian military, which had been bombarding Russia's forces on the island relentlessly, said the Russians were forced out, fleeing in two speedboats.

President Volodymyr Zelenskyy hailed the Russian withdrawal from Snake Island as the strategic victory.

"It does not yet guarantee security. It does not yet ensure that the enemy will not come back," he said in his nightly video address. "But this significantly limits the actions of the occupiers. Step by step, we will push them back from our sea, our land and our sky."

In contrast, however, Ukrainian forces were desperately hanging on against Russia's superior firepower in the city of Lysychansk.

Russian artillery shelled from different directions while the Russian army approached from several sides, regional Governor Serhiy Haidai said on Ukrainian television.

"The superiority in fire power of the occupiers is still very much in evidence," Zelenskyy said. "They have simply brought in all their reserves to hit us."

Russian forces have been trying to encircle Lysychansk since they captured Sievierodonetsk, on the opposite side of the Siverskyi Donets River, last week after weeks of heavy fighting.

Ukrainian forces in the "south" district of the Joint command of the Ukrainian armed forces killed 35 Russian servicemen and put out of action two tanks and four armoured vehicles, according to a Ukrainian military statement on Facebook on Friday.

"The Ukrainian armed forces are not only holding defence lines but also engaging in successful operations aimed at liberating occupied towns in Kherson region from the invaders," Kriviy Rih regional Governor Oleksandr Vilkul said on Telegram, adding Ukrainian troops had taken back the town of Potyomkin.

The battlefield claims could not immediately be verified.

The United Nations said on Thursday that some 16 million Ukrainians require humanitarian aid and more than six million are internally displaced.

NATO leaders meeting in Madrid this week pledged to back Ukraine for as long as necessary, modernising the country's army to help it resist Russia’s invasion. The military alliance also updated its strategic plan to name Russia as the biggest "direct threat" to Western security.

NATO has also approved membership applications from Finland and Sweden and announced a massive boost in troop numbers along its eastern flank.

Several Nato member states have announced new military aid for Ukraine: British Prime Minister Boris Johnson has pledged an extra £1 billion (€1.16 billion) and Joe Biden has pledged a further $800 million (€765 million).

French President Emmanuel Macron spoke of a shake-up in military planning in his country, stressing that "we must now, entering a period of war, know how to produce certain types of equipment faster and stronger". — Euronews