Russian forces fired cruise missiles at the southern Ukrainian city of Odesa overnight and shelling destroyed homes in the eastern Donetsk region early Wednesday, killing at least six people and injuring more than a dozen others, regional officials said.

A Ukrainian military spokesman said Russian forces have stepped up aerial strikes in their more than 15-month war against Ukraine, just as the country's troops have reported limited gains in an early counteroffensive.

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In the east, Donetsk regional governor Pavlo Kyrylenko wrote on Telegram that at least three people died after shelling destroyed seven homes and damaged dozens more in the cities of Kramatorsk and Konstantinovka.

In Odesa, three employees of a food warehouse were killed and seven others injured in a strike that damaged homes, a warehouse, shops and cafes downtown, he regional administration said on Facebook. Another six people — guards and residents of a neighboring house — were injured.

Searchers were looking for possible survivors under the rubble, it said.

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The attack on the port city, launched from the Black Sea, involved four Kalibr cruise missiles, three of which were intercepted by air defenses, the administration said.

Andriy Kovalov, a spokesperson for Ukraine's General Staff, said Russian forces have increased missile and aerial strikes on Ukraine.

In a briefing, he said strikes on the Kharkiv, Donetsk and Kirovohrad regions, in addition to the Odesa region, involved Kh-22 cruise missiles, sea-launched Kalibr cruise missiles, and Iranian-made Shahed drones. Nine were intercepted.

Kovalov said Ukrainian forces made advances on several fronts of the roughly 1,000-kilometer (600-mile) front line, and fighting was continuing in or near at least two settlements in the eastern Donetsk region. Russia has occupied and controls nearly one-fifth of Ukrainian territory.

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Britain's Ministry of Defense, which has regularly issued updates on the conflict, wrote on Twitter that southern Ukraine "has often been more permissible for Russian air operations" compared with other parts of the front.

Separately, the mayor of the central city of Kryvyi Rih, President Volodymyr Zelenskyy's hometown, said the death toll from a Russian strike a day earlier that hit an apartment building had risen to 12.